My fiancé has a 19 year old son that is severely autistic and unable to speak. He and his ex-wife have been advised to seek guardianship. His ex is the custodial parent at this time and wants sole guardianship. If he agrees to this will he lose any rights as the father? Will he have a right to any decisions made for his son, as in, putting him in a residential facility? How does this affect his parental rights?

ANY question on law needs to include your general locale as laws vary by area. I'm assuming since the boy is now legally an adult, that is why they need to seek guardianship. If the mother is granted sole guardianship, then she will have sole decision making power. However, he can still be allowed visitation as part of the guardianship agreement. Granting her guardianship doesn't take away his rights, but if she is granted sole guardianship and he disagrees with any decision she makes, he will have to go back to court to modify the guardianship order.