My boyfriend’s daughter has autism and I am unwilling to take on the responsibility

I’ve been with my boyfriend for almost 5 years and he did not tell me his daughter has autism for the first 2 years of our relationship. She is 9 and he claims they didn’t know up until maybe 2 years ago. He now wants to do family activities and live together but I don’t think it’s fair to force the bond on my daughter who is 10 years old and does not have autism. I am also not ready for the responsibility and lack the patience required for a special needs child.

My bf and the child’s mom are still in denial and not getting her the proper care/support needed. Am I wrong for feeling the way I do? I feel it was sprung on me and I wasn’t really given the choice in the beginning. It’s a lot to take on, I can tell my daughter is uncomfortable, and I don’t want the responsibility. TL;DR