In a universe where soulmates exists, they share their thoughts and emotions but the bond is only complete after the two people have met and both agree to it. Basically, Finn and Kylo are soulmates, Finn figures it out before Kylo, and maybe that's also part of the reason why he leaves the First Order. Kylo finally knows after Starkiller Base and is torn over it, Snoke taught him that having a soulmates is weakness, and he implies Kylo should just kill Finn. Through their Force bond, Rey finds all this out and tries to help them both.

Give me some angst but I'd like a somewhat happy ending