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.
And, if you want to use nicknames, like mom, in your commands, you can establish relationships. On iOS devices, you can simply open Siri and say my mother is 'Jane Smith'.. Or, when you edit a contact, scroll down to Related Name and hit the +. The first, and default, relationship is mother.