Explaining death to young children is difficult. There is a small, easy to read childrens book called 'Water Bugs and Dragonflies', Which uses a simple, very gentle metaphor to explain death. I would...
tell him/her the reason why you gave them up (e.g i was very young when you were born, too young to look after you and give you a proper life, the life you deserve, so i had to give you to someone...
yes like when :
his father is AA RH- and his mother is OO RH- he will be AO RH- (A-). his father is AO RH- and his mother is OO RH- he may be:
AO RH- (A-) OO RH- (O-)
So, the most one is ( A-) ....