Doctor Belasco said
My concern is that it would be in my character's interest to ally himself with a powerful family. He might consider yours a sinking ship. Obviously there's a plot here - he might have a history with you, or defect away from you over the course of the RP. Don't expect to keep him :P
Sounds delicious! Without a doubt, my family is a sinking ship. Many members of the family know this, but do not want to give up. In a sense, this is why they excelled in alchemy.
The high-end witch society is a backstabbing one and being in the ring for so long, I would assume my family knows the game, thus, take precautions to who they take in. Since they also have symbol magic (which they will never teach anyone, but their bloodline), they could probably brand outsiders before letting them in their inner circle. So when and if they do---…
… *Thinks about it*
On second thought, it might be safer for your character to be unrelated to my family. If they did brand outsiders using symbol magic, then (based on what I can gather of your character so far), he probably wouldn't risk joining a "sinking-ship" family to learn all that he can from them and betray them, only to be possibly killed by the brand. My family may be a sinking ship, but it is a very dangerous one ;) Although, that can also be a sub-plot (your character carrying the cursed brand, which he managed to keep dormant for awhile and is trying to find away to be free from it).