Multi-purpose best boy

The one boy who will take on any role in a girl's life. Usually an attempt to be unofficially a permanent part of her life.
When you're taken, he often is the best guy friend.
When you're dating a loser, he breaks you both up.
When there's trouble, he's the big brother.
When you're single, he will often date you as long as you have no one. Occasionally can turn into very intense flirting.

Can be sexy, kind, funny, talented, stylish, passionate, romantic, even adoring or very attractive.
Quite often is charming and extremely kind but has a low chance of being married due to a complex issue in his life.
Every girl needs a multi-purpose best boy.