My mother did this 27 years ago. She never changed her name when my parents got married, and when my older sister was born they gave her my mothers last name. I got my fathers, and they flipped a coin for my little sister (my father won). Myself and my partner already discuss whose last name will be used when we decide to have children. One interesting point to make to people who question your decision, is what same sex couples decide on. It’s not automatically the mans last name with no discussion involved.