You can foster closeness and increase intimacy by having meaningful conversations. Those conversation might include the following six topics: gratitude, nostalgia, advices, sharing, getting to know each other's preferences and commonalities. The questions below will help you address those topics and therefore, could potentially enhance your level of connection.
1. What do you miss about being a kid?
2. If someone gave you enough money to start a business – no strings attached – what kind of business would you want to start and why?
3. Tell me about a relationship issue you’re having, and ask me for advice on how to fix it.
4. If you could go back in time, what’s one piece of advice you’d give to your younger self?
5. What’s something you want to do in the next year that you’ve never done before?
6. Tell me three things that happened in the last week that you’re thankful for.
7. What’s your favorite memory we’ve shared together? Gimme as many details as possible.
8. What makes you happy?
9. Who or what has changed your life?
10. How do you best connect with others?
11. Are you a giver, a taker or a matcher? Are there areas in your life where you act like one type, and other areas where you act like another?
12. What are the five most important things on your bucket list?
13. What matters most to you?
14. What’s some of the best advice you’ve ever gotten?
15. What’s your ideal weekend?
16. If you could take a year-long paid sabbatical, what would you do?
17. Who do you trust?
18. What are five things you’re thankful for right now?
19. If a genie granted you three wishes right now, what would you wish for?
20. What’s the craziest thing you’ve ever done and would you do it again?
21. What’s your favorite family tradition?
22. If you could enter a time machine, what time period would you go to?
23. What’s your favorite quote?
24. What do you value most in a friendship?
25. Tell me your life story in four minutes, with as many deets as possible.
26. What’s something I’ve done for you that you’re grateful for?
27. What do you want your legacy to be?
28. Let’s alternate sharing three positive characteristics of each other.
29. What are your biggest goals for this year? How will you work to achieve them?
30. Where was your favorite place to go as a child and why did you love it there?
31. Tell me about a challenge you’ve been having at work or school, and ask me for advice on what to do about it.
32. What was the first thing you bought with your own money?
33. What are you curious about?
34. What are your top three strengths? Which strengths do you look for in a friend or partner?
35. Name four things we have in common.
36. What are your favorite three topics to talk about?
37. What’s your earliest memory?
38. How do you express gratitude towards others? Give me an example.
39. What are the top three ways to express your love in friendships and in relationships?
40. In what situations do you feel most comfortable sharing your perspective?
41. Who’s someone you really admire?
42. How do you like to be comforted when you’re upset?
43. What would you do on your “perfect” day?
44. In 10 years, how would you like to describe your life?
45. If you had $100,000 to give to any cause which cause would you choose and why?
46. Where are the top three places you want to travel to some day, and why?
47. If you could have any job you wanted, that would it be?
48. Tell me about a day you had that you’ll never forget.
49. If there were 26 hours in a day, what would you do more of?
50. Is there something you’ve dreamed of doing for a long time? Why haven’t you done it yet?
51. What moments or events during your childhood shaped who you are now?
52. What do you think about most? 
To make sure though that you are going to develop a stable marriage, it’s important to be quite direct and open about issues, secrets and other intimate questions, because otherwise you’ll have to face them during your marriage eventually.
- Did your family throw plates, calmly discuss issues or silently shut down when disagreements arose?
- Will we have children, and if we do, will you change diapers?
- Will our experiences with our exes help or hinder us?
- How important is religion? How will we celebrate religious holidays, if at all?
- Is my debt your debt? Would you be willing to bail me out?
- What’s the most you would be willing to spend on a car, a couch, shoes?
- Can you deal with my doing things without you?
- Do we like each other’s parents?
- How important is sex to you?
- How far should we take flirting with other people? Is watching pornography O.K.?
- Do you know all the ways I say “I love you”?
- What do you admire about me, and what are your pet peeves?
- How do you see us 10 years from now? 
52 Questions For Deeper Conversations
When's the last time you had a meaningful conversation? Or improved your relationship with your loved one? Discussing big topics, rather than small talk, is crucial to maintaining a deep connection. Here are 52 questions that will deepen your relationship with your loved ones, according to science.
13 Questions to Ask Before Getting Married
When it comes to marriage, what you don't know really can hurt you. Whether because of shyness, lack of interest or a desire to preserve romantic mystery, many couples do not ask each other the difficult questions that can help build the foundation for a stable marriage, according to relationship experts.
Gottman found that happy couples differ from unhappy couples in conflict discussions in the following ways:
To have a healthy relationship Gottman created the “The Sound Relationship House” – a tool that helps “increasing closeness and friendship behaviors, addressing conflict productively, and building a life of shared meaning together.” 
“At the heart of the Seven Principles [of Marriages] approach is the simple truth that happy marriages are based on a deep friendship.” (Gottman)
Finkel, a professor for psychology and management, also compiled a few things to keep a marriage on track:
- Be empathetic and have open communication.
- Show Appreciation.
- Share your spouse's joy.
- Diversify your social portfolio.
- Hold hands and be affectionate. 
"Each relationship develops its own unique culture over time - its own norms, beliefs, and jokes. […] Spouses in a successful marriage can leverage their shared culture to achieve a sort of emotional shorthand that can help them stay connected even when time together is scarce." (Finkel)
Once the honeymoon phase wears off, couples have to actively work on their marriage. Gottman's has a few advices based on his observations of happy couples on how to enhance and stabilize your marriage including the following:
- Seek help early.
- Soften your startup.
- Learn to repair and exit the argument.
- Accept influence from your partner.
- Focus on the positives. 
What's the secret of arranged marriages?
Based on his research Gottman can predict if couples will get divorced at some point based on four behaviors. Acknowledging them is the first step to reverse these patterns of behavior and turning them into constructive and positive ones instead. 
Another thing that helps making marriage last is to have constructive communication skills. During conflict couples one should focus on three important aspects:
- Use ”I” Statements.
- Explain the “what” you are complaining about.
- Effectively communicate what you need how your partner can be your hero. 
"Each potential relationship has its own set of inescapable recurring problems. [...]There is value, when choosing a long-term partner, in realizing that you will inevitably be choosing a particular set of unresolvable problems that you'll be grappling with for the next ten, twenty, or fifty years." (D. Wile) 
- Lemonade. (2018). 52 Questions to Bring You Closer Together. https://www.lemonade.com/blog/creating-meaningful-conversations/#methodology
- Stanford, E. (2016). 13 questions to ask before getting married. https://www.nytimes.com/interactive/2016/03/23/fashion/weddings/marriage-questions.html
- Gottman, J. M., Coan, J., Carrere, S., & Swanson, C. (1998). Predicting marital happiness and stability from newlywed interactions. Journal of Marriage and the Family, 5-22.
- Gottman, J. M. (2018). The Science of Love | John Gottman | TEDxVeniceBeach. https://www.youtube.com/watch?v=-uazFBCDvVw
- Gottman, J. M., & Silver, N. (1999). The seven principles for making marriage work. New York: Three Rivers Press.
- Finkel, E. J. (2017). The All-or-Nothing Marriage: How the Best Marriages Work. New York, NY: Dutton.
- Gottman, J. M. (2017). The Top 7 Ways To Improve Your Marriage. https://www.gottman.com/blog/the-top-7-ways-to-improve-your-marriage
- Iyengar, S. (2011). The Art of Choosing. New York: Twelve.
- Myers, J.E., Madathil, J. &Tingle, L. R. (2005). Marriage Satisfaction and Wellness in India and the United States: A Preliminary Comparison of Arranged Marriages and Marriages of Choice. Journal of Counseling & Development, 83.
- Gottman, J. M. (2018). Making marriage work. https://www.youtube.com/watch?v=AKTyPgwfPgg
- Gottman, J. (2011). How to Complain Without Hurting Your Partner. https://www.youtube.com/watch?v=bShsyKUFjKE
- Wile, D. B. (n.a.). Dan’s Quotes - ABOUT COLLABORATIVE COUPLE THERAPY. https://danwile.com/my-blog/my-quotes/
- Gottman, J. M. (2018). The Truth About Expectations in Relationships. https://www.gottman.com/blog/truth-expectations-relationships/
- Barker, E. (2014). The Science Of 'Happily Ever After': 3 Things That Keep Love Alive. https://time.com/62029/the-science-of-happily-ever-after-3-things-that-keep-love-alive/
- Gottman, J. M. (2011). What to do About "Unsolvable" Problems. https://www.youtube.com/watch?v=PpK8p3wTta4&list=PL7A9EA9AD9CEC5B1B
More on the topic:
- Chapman, G. D. (2010). The five love languages. Walker Large Print
- Gottman, J. M., & Levenson, R. W. (1992). Marital processes predictive of later dissolution: behavior, physiology, and health. Journal of personality and social psychology, 63(2), 221.
- Gottman, J. M., & Levenson, R. W. (2000). The timing of divorce: Predicting when a couple will divorce over a 14‐year period. Journal of Marriage and Family, 62(3), 737-745.
- Johnson, S. M. (2013). Love sense: the revolutionary new science of romantic relationships. First edition. New York: Little, Brown and Company.
- Perel, E. (2006). Mating in captivity: Reconciling the erotic + the domestic. New York: HarperCollins.
- Stillman-Berger, S. (2019). The Secret to Having a Happy Marriage. https://www.oprahdaily.com/life/relationships-love/a28186035/how-to-have-a-happy-marriage/
- Gottman Institute. (2021). Small Things Often. Podcast. https://open.spotify.com/show/0e1KN182aQsnx4qk1nN3Mf?si=eONGzlRdTaCcqYqdtRE7mA&dl_branch=1
- Relationship Alive!. (2015). 01: John Gottman – How to Be a Master of Relationship. Podcast. https://open.spotify.com/episode/5KIqYnz2Zvc8K0N0WP2uP0?si=hTzjJMLPSWiauw5bI6ZVkA&dl_branch=1
- Tashiro, T. (2014). The Science of Happily Ever After: What Really Matters in the Quest for Enduring Love. Harlequin.
- Taylor-Cummings, A. & Taylor-Cummings, J. (2019). 4 Habits of ALL Successful Relationships. https://www.youtube.com/watch?v=o4Y5Mr8rZ9A
- Carstensen, L. L., Gottman, J. M., & Levenson, R. W. (1995). Emotional behavior in long-term marriage. Psychology and aging, 10(1), 140.
- Perel, E. & Miller, M. A. (n.a.). Rituals For Healthy Relationships At Every Stage. https://estherperel.com/blog/rituals-for-healthy-relationships