In addition to the proteins (agglutinogens) existing on your red blood cells, other genes make proteins called agglutinins (a-GLOO-tin-ins) that circulate in your blood plasma. Agglutinins are responsible for ensuring that only the blood cells of your blood type exist in your body.
Older children and teens are unlikely to start calling a stepmom mom or mother partly because of their fear of disloyalty to their biological mom. It is vital for all parties involved -- biological parents and stepmom -- to support their child's choice of what to call the stepmom.
Sometimes you just fall in love with babies. I adopted my friend's son as my nephew and the kid calls my parents his grandparents because his sperm donor (dick doesn't deserve to be called dad) and his parents aren't part of his life. The kid is 3 and I love him with my whole heart. I'm glad your mom took care of you!