Was this a weird thing for my fiancé to do ?

Hi! Earlier I was in the car with my bf and we were talking about hypotheticals , randomly I asked him if he hadn’t met me ever and my sister hit on him , if he would date her and he said yes. I found this weird and idk how to feel abt it. I know he wouldn’t do anything with her , and I know he wouldn’t ever cheat on me. We are getting married in a month , so I’m like ?? I also know it’s a hypothetical question but, i feel that is something you shouldn’t say. My sister is super good looking , but it kind of took me by surprise. Do you guys think this is a reason to break up ? Or is it my fault for asking a dumb question LMAO