If they’re not your best friend, who is?

How do you view a partner that is supposed to accompany you for the rest your their lives? Do you give much importance to who it is and if you have the best chemistry and friendship? Or do you think that as long as you have someone who fulfils a relationship role and status, you are okay? I wanted to explore this dilemma more and share my view on how important I think a friendship between lovers it.