4 year old son... 😬

Earlier my boyfriend, son and I were talking about our neighbor just having their little baby boy and everything... Well then our son ask "when is my sister going to get here?" and I said hopefully in a few weeks she'll be here, then he asked "how are the doctors going to fix your belly when she gets out" and I had to explain to our son that she isn't going to come out of my belly and explained where she'll come out of. My son is pretty mature for a 4 year old so that was the end of that questioning. It was quite for about 5-10 minutes then he looks at his dad and I and goes "so how did my sister get in your belly?" I literally couldn't answer him so I just looked at my boyfriend and was like okay your turn to answer... Lol