Common core values are what make close relationships close. But, the tricky thing is that often you learn what they are by taking a step back at what makes relationships work, and why other relationships didn't.
Having well-defined core values and forming relationships with others who share those values is WHY we feel like we found "our tribe" or "our family." (This is often why our actual family doesn't feel close, because even though you share biology, you may not share core values.).
Knowing what's important to you and why is a big step to finding people who you fit with. For instance, some of my TOP values are radical honesty, vulnerability, self-awareness, curiosity, and growth. These are the things I believe are the most important things in life. So I may not be very close with someone who doesn't like to open up or never asks "why" about anything. I may be able to enjoy this person here and there, go to a movie or something, but we wouldn't be "close."
Core values are what you believe is important about life. For example, If you have a value for happiness, but you're married to someone who values security much more than happiness (this is SO common by the way) then you just may not understand each other very well.
When you define your deep core values, you are one step closer to finding your soul brothers and sisters. It's so worth it.