That sucks. I can 'sort of' relate. After my last sister moved out when I was 9, I was the only child for the next 10 years till I was an adult. At first it was nice, but then I missed the bickering I had with my sisters.
If you look at the current show, Bart's is the older, lead child whereas Eric was the youngest and he had Bart giving him advice on how to be a snarky little boy, but one who is from a decade later where girls aren't cootie machines.