you can know by
blood group testing only -
Mother A+FATHER A= A or O
MOTHER A+FATHER B=A,B,AB,O
MOTHER A+FATHER AB=A,B,AB
MOTHER A+FATHER O= A,O
MOTHER B+FATHER A=A,B,AB,O
MOTHER B+FATHER B=B or O
MOTHER B+FATHER AB=A,B AB
MOTHER B+FATHER O=B,O
MOTHER AB+FATHER A=A,B,AB
MOTHER AB+FATHER B=A,B,AB
MOTHER AB+FATHER AB=A,B,AB
MOTHER AB+FATHER O=A,B
MOTHER O+FATHER A=A,O
MOTHER O+FATHER B=B,O
MOTHER O+FATHER AB=A,B
MOTHER O+FATHER O=O
so follow and check it (Thanks)