Nasab

Q: Please could you answer the following question I need the info to settle a dispute. I was taught that when a person gets pregnant out of wedlock and gets married to the person the child is still considered illegitimate if born fewer than 6 months after the marriage. My sister-in-law says that if the mother has 7 children altogether that it will then make the first born halal. Could this possibly be true? I battle to grasp the logic. Please help.

Q: My big brother passed away. I adopted his son. Can I use my name as his father as the child does not know about my big brother he only know that I am his father?

Q: We had an affair and had an illegitimate daughter from that affair. After that we got married. Now my daughter is 20 years old. She does not know anything about this and she is going to marry soon. My question is can I be the Wali (guardian) to my daughter? If not who can be the Wali?