Explained to him that its best left alone as she has no idea about her bio father or anything to be honest. And this could/would just cause upset for her and her family that they really could do without. That he has plenty of relatives to be going on with and that if she is ever told then she will remember this and be able to get in contact with him then.

He said....... Ok mum if that's what you think then thats what I will do.

I am so proud of him for not arguing about this.