Adding Minions to a PC

[Thrawn82]

I am running the Blood Lords adventure path, and i have a player who is going all in on the animate dead spell and create undead ritual.

I've noticed there is a neat system for summon monster/summon nature where you can select a minion attached to a PC that the spell can then put on stage during combat. This feature doesn't seem to be in place for Animate Dead or Create Undead.

Is there a way for me to add that feature manually to his character?