Do the father and mother have a right to the blood money you received for the death of your son, given that you paid off your debts with it and donated the remainder, and that the mother is pregnant with another heir?

The blood money (Diyah) is for the heirs of the deceased only. The grandfather of the deceased (his father's father) does not inherit if the father of the deceased is alive, and the grandmother of the deceased does not inherit if the mother of the deceased is alive.

So, if you are the father of the deceased, your father has no right to claim any part of the blood money. And if the mother of the deceased (your wife) is alive, your mother also has no right to the blood money.

If the heirs are limited to those mentioned, and the mother of the deceased is pregnant, then the inheritance (blood money) is divided into six shares: the mother takes one share, the father takes four shares, and one share is put on hold. If it turns out that the pregnancy is a single individual or is stillborn, the mother takes the reserved share. If the pregnancy results in live birth and is more than one, the father takes the reserved share. The full sibling (of the deceased) gets nothing because they are completely excluded by the father. It is not permissible for the father of the deceased to conceal the matter of the blood money from the mother of the deceased, as she has a right to it.