Husband and wife

Was looking at some old photos, am just wondering, life is weird. I mean, how did we end up with the person we are with now? is it fate?

I mean, so many people came into our life, some people had a few boyfriends or girl friends before they got married, so why this person you choose to marry? is it fate?

on the other hand, there are some people whose paths you will cross later in your life, then how? why did fate bring both of you to cross path and yet can't be together?

I don't understand life.