C was 22 months when D was born so he knew I had a baby in my tummy and was happy pushing his own baby round in a stroller but didn't really get into pretend play back then. My neighbour was pregnant with #2 at the same time and her DS1 is almost a year older than mine. He would talk about a baby in his tummy, he had another wee girlfriend his age who was also expecting a baby sister and SHE had a baby in her tummy too

I think it's just an age thing and I wouldn't worry about it at all! They don't really get the concept of boys and girls being "different" at this age

My 2.5yr old has been saying "Good boy, Mummy" to me all day today LMAO!