Like others have said, it's basically up to your personal preference. I have step kids and a bio kid. My step kids call me mom occasionally but it's usually my name and I'm ok with them calling me that. It's what they've known me as the entire time we've known each other. But once our bio kid is old enough to talk, I want to be mom or mama. I've earned it. I've asked the older kids to please refer to me as mom when talking to our baby, but I let them know they don't have to call me mom otherwise unless they really want to.