I am an only child and i wuld never just have one. However i understand thats not always possible for everyone.
Looking back i realise i was always quite grown up as a child, you always have adult attention and spend alot of time playing, being around other grown ups. Although i did have 13 cousins and lots of friends too.
The worst times were school holidays although i was lucky that we could afford to go away, but i always remember trying to find friends to play with and asking my dad to help me find one as soon as we got to the hotel. We used to goout to dinner and i'd see other kids all playing, chatting at the table and as much as i loved my parents it's alwaysmore fun to have children to play with.
The thinkg i have found since being a parent of 2 is that they play together, so you don't need to invite friends over all the time, and when you go on holiday or out to dinner they have anaturalplaymate, evenif they do argue sometimes.
The other thing i notice wheni have onlies over to play with dd (5) is that they only want to play with her and not her brother too(nearly 3). I can see that i was a bit like this as a child. You havegone to play with your friend so why should the little one join in, but when you are a family of more than 1 they do expect that friends come over toplay with all not just the inviter.
I also love watching them sharing experiences together, getting excited over christmas together, things that me and dh are there for too, but the excitement to share with another child.
As an adult i would love a sibling, i've always wanted one.Luckily i have a fab best friend who i've known for 22 years so she is my sister (even tho she has her own too)
I had a horrendous birth with dd so we waited nearly 3yrs before having ds (elective section!) but it was so worthit. Tobe honest i'd have another 2, but dh is happy as we are....