Nothing really changed in my house when I had DS 3, my first 2 boys are only 16 months apart and have a great friendship, so if anything when I had No 3 they had each other for company so didn't really notice if I wasn't giving them as much attention. As number 3 got older he just fitted in with the older boys (he thinks he's 6 too). It did help that No 3 was an easy baby. Although now that the older 2 boys are both at school I can tell that he is quite lost without them.