Being the oldest (I'm male by the way but issues should be similar) and not having a relationship with my father I always turned to friends in the neighborhood to look up to though I don't know if they knew it. But there was one guy, who as it turns out was older and had no little brother and we became good friends.

Maybe there's an older friend you could hook up with.

Aside from that my mentor's ended up being heros in books. Sounds a bit funny at first, but there are several great books in which the hero became like my older brother.

Everybody will think I'm a little "off" but I always looked up to Holden Caulfield from "Catcher in the Rye" and Winston Smith in "1984".

And my big sis was Sissy Hankshaw in "Even Cowgirls get the Blues"

Actually, these were great characters and I don't think it's so strange all of a sudden.