Ok everybody, a quick lesson in blood groups:
Each of the four blood groups are made up of 2 of 3 possible characters. 0 (zero), which has no antigens, A (A antigens) and B (B antigen).
This gives us
- blood group 0 (00)
- blood group A (0A or AA)
- blood group B (0B or BB)
- blood group AB (AB)
You pass one of those two characters on to your child, as does their other parent.
00 + 00 =00
0A + 0A = 00, 0A or AA
0A + 0B = 00, 0A, 0B or AB
AA + BB = AA, BB or AB
00 + AA = 0A or AA or 00
00 + BB = 0B, BB or 00
00+ AB = 0A or 0B
It‘s possible to have a different blood group from one or both parents, but there are certain combinations that just aren’t possible, like you being blood group B and both parents being A, or being AB with a 0 parent.
Then you have the Rhesus Factor which gives you a + or - on your blood group. Most people are positive as - is recessive. But 2 - parents can’t produce a + child.
So blood groups is another way different parentage can come out.