My first liittle boy was only 4 months when we found out we were expecting our little girl. Now we are expecting baby #3 in two weeks. So we will have 4 yo, 3 yo and a newborn.
It's hard sometimes with my son and daughter being 13 months apart but I'm happy they are close together. You can't separate them for nothing because they have such a strong bond with one another. Congratulations on your upcoming arrival.