Can you change your babies last name without a paternity test/adding father to birth certificate ? PLEASE READ WHOLE PARAGRAPH

I was drugged and assaulted by multiple people resulting in my pregnancy w my daughter so her biological father is unknown but my boyfriend has always raised her & he is her father (shes 9 months) I posted a question here the other day about wanting to add him to the birth certificate but from what ive gathered they will require a paternity test & obviously hes not the bio father. So that brings us to wanting him to legally adopt her but ive been told the bio father has to sign off rights and obviously theres no bio father. So am I able to just change her last name? We are having our 2nd baby in October and want both of our children to have the same last name