Isn't this just more evidence that Cavs should not be crossed with Labradors?Cavaliers are 12-13" tall and 13-18lbs. Labs are 22–25" and (60-130lbs) I doubt your taller sibling is twice your height and six times your weight.
I've got my Grandfather's blood type. It's one of the rarer ones. Neither of my parents had it but if either of them had been type O, I would not have been able to have what I've got. I don't know what my siblings blood types are.