NOOOO
He dislike poison types? So sad
I'll think about one and then edit this post to give him one cool mon
Edit: I really liked that Trubbish, his name would be I'mnotrash.
So, he'll get something close to it =D
Your brother will get Imnotdark, the Pawniard
He hates the fact that: He is an undead, and, as an undead, the OBVIOUS would he be GHOST/Steel(as a soldier, steel is the obvious second option)
So, never in his life(whoops...dead) he can use a dark type attack(he is not a dark type. Period.)
He wants to kill every dark type mon he faces, so, once he find a Dark Type mon, he can never switch out.
He thinks that another ghosts are his friends(he is a ghost, so, no ghost REALLY wants to do something with him...), so he needs to switch out when he find a friend.
After killing 10 Dark Types(creepy bastards) AND meeting 3 friends(different species of) he can evolve.
After evolve, the restrictions continue.
Hope he likes it