Is it wrong to love someone you've known your entire life?

Why would that be wrong? If anything it's GREAT! Because you know that person dearly, you understand them and you can trust them better.

Nope. I'm married to someone I've known my entire life, my parents have known each other their entire lives, and one set of my grandparents knew each other their entire lives. I find it fun how both sides of the family can share stories with my kids about the other side. I like how I can tell my kids what their daddy used to be like when he was a little boy. Healthiest relationships are where a person can really think of their partner as their best friend.