I'm the youngest of 3. My brothers are 3 and 6 years older than me. I didn't feel like I missed out on anything. DH however was adamant he didn't want 3, it must be 4 after being the middle child of 3. He doesn't care but felt like the "middle child" - his younger sister got everything and all the attention, his older brother wasn't the brightest so DH just did his own thing. His family dynamics are still the same now that they are adults. We have 4 children which seems to work well, 1&2 play and 3&4 play, not many arguments and they're all close together so have similar interests.