My child who was 1-1/2 at the time did not take well to the 3rd child, but it was boy so that made him the middle child and a middle boy to boot. He was fine when I had my 4th which was a girl but he was 3-1/2. However, the 3rd had no problem adjusting to a fourth child. As to changes, beware that you do not have enough hands by yourself for 3 kids. Does not seem like a big deal but it was. Things will work out so do not fret. The other thing is that you need to count noses as they grow more independent. We left one at home for a very brief time and we left one in a closed van in the summer, very scary. I thought my husband him the child, and he thought I had the child. Different kids each time, thank goodness.