Blood Type Q: AB+ mom, not sure about dad, what possibilities?

Question

I was sitting in a boring meeting, and started thinking about our upcoming blood drive, which started me thinking about blood types. If I am AB+, that means my brother and sister both are too, right? So if my sister is AB+, and I don't know what her husband's type is, what are the possibilities for my niece and nephew? (I'm a nerd, I know. Most people just doodle during meetings.)

Answer 1

It can come from either parent.  I am an O+ and my fraternal twin brother is AB+.(Born at the same time but come from different eggs.  I am also a girl)  I am not sure what the odds are if you dont know your Dad's.  When you give blood, they will send you a card back stating your blood type.

Answer 2

If your mother is AB+ and your father's type is unknown, you and your sibs could have any combo of blood type.  My parents have different blood types and each type is rougly divided among all my sibs.  

With your mom AB+, suppose your father was O-.  This would introduce all blood types and Rh factors.

Answer 3

this should help you out.

Answer 4

You can't draw the conclusion that your siblings are all AB. There are several different crosses that will give AB blood, and these can produce different combinations of offspring:

AO + BO --> AB, AO, BO and OO

AA + BO --> AB + AO

AO + BB --> AB + BO

AA + BB --> AB

Only in that last case will all the siblings have to be AB, and in order to know which is the case, you have to actually determine their blood types or better, your parents' blood types.

The + is a different trait and it is inherited as a dominant. But you could be ++ or +-. IF both your parents were +-, the some of you might be --.

Only if you know your sisters complete blood type AND her husband's complete blood type can you really predict the blood types of their kids.