Age differnece between children? have u had more than u thought u wanted?

I always said I wanted 2 [boy and a girl] but now I don't know if I'd be happy with just this one. I've also considered adoption. There is an 18 month age gap between my sister and I, which sometimes worked well and we played happily together, other times we fought like cat and dog. There is a 29 year age gap between my Dad and his sister [wow] and they are not close at all.