Q: I have a son and daughter. I do not know what was in my daughters head but she did some haram things with her brother that is younger by 3 yreas. Does this haram action affect our nikah according to imaam shafee? me and my husband that is? (text)
A: Under general conditions, your nikah is not affected by what your children voluntarily do to each other.
*Separate them till the matter is fully resolved. Try to protect your son by having open-door polices. Example: no more alone-time in the bedroom together, always have the door open when they in the room, etc. Have an open communication line that enables you to know what is going on in their lives.
Allah Certainly Knows Best.