So there’s a character that I have a lot in common with. Like, same physical appearance and our pasts are similar and so are our personalities. I’m not sure if I am fictionkin or not. But I’ve kind of become obsessed with him. What is going on?

Likely what is going on is that you are fixated on the character because you perceive so many similarities between you and the character.

It is possible that you are kin of them, but looking like a character, or having a similar life story as a character does not make you kin, nor does liking a character a lot.