Hmm... *ponders*
Well. As for attractive, sh's been sheltered from men her enitire life thanks to her father. So just a close to norm handsome will do. Oh! And Icy hair! You know how hers is an Icy blue? I thaught it'd be fitting for him to have a paler, whiter color for his hair. It doesnt have to be though. It could be as ebony as youd like it, or any other color for that matter.
Powers? He needs to be strong, thats definately needed. Why? Because Tildia may be brave. But strength isnt her best attribute. And as for magic, i'd rather he not have too much. Because Tildia needs his strength, and he needs her magic. I need it to be a bit balanced as to why they even bother to stay around each other before falling in love.
Personality... He needs to be older than her (older than 19), so he also needs to like to take charge of things. Like when Tildia has those moments in battle whered she'd rather stop and gawk at her foe, rather than attack. He needs to be the one that will yell, "Tildia behind you!" Or, "PAY ATTENTION!" Needless to say, he's probably gonna be yelling at her alot. ^_^
As for his history. It can be anything, as long as it envolves him being given away before Tildia was born. And him figuring out that he had been born with only very little of his fathers magic, and none of his mothers 'holiness'. Oh! almost forgot! Father = Human Mage, Mother = Fallen Angel. Therefor Tildia is a human born angellic mage, but her brother somehow only got the 'human' and the 'mage' part. Maybe he took after his father? O_o
Oh! And of course you reserve the right to twist him to your liking. ^_^