Is there a spell or ritual that will let you choose who your demon parents are?
Hmm, that is a little weird question first, talk with diviner, he could tell you about your parents because they can be Demons, like my family and me
If you develop a good working relationship with a spirit, you may ask them to adopt you, and wholly or partially sever links to one of both of your human parents.
But not as one single spell I wouldn’t think, it links you in all kinds of ways so the spirits you work with most, are most likely to undertake this and anything that seems to simple and easy to be true, probably is.
It is a HEAVY responsibility, and will affect your entire bloodline going forward.
Agreed, make sure this is what you want and that you like your chosen parents. Once you got em you’re stuck.
Definitely choose the wording with care, this has some stuff on it I have found so far for pact-making: