So my daughter is 11 in July. I've just started TTC (last night lol), and so the age gap is going to be at least 11 years between her and her brother/sister.
She's been an only child for so long, and while I expect the next child will be treated pretty much exactly the same way she has, I'm a bit nervous about how she's going to go with it. She's a little bit greedy when it comes to my attention and always has been - potentially as her father, who was in her life full time until 2.5, abandoned her when she was 3.5 and moved overseas, only to hear from him a few times afterwards when he informed her that he had a new baby son (which crushed her - she was only a preschooler at the time and cried, "But why? He had me! He could have had me!" which both broke my heart and made me feel particularly murderous), and hasn't spoken to her at all, in any way, since 2010.
She has my partner in her life though... he's been around since she was 3 and they have a fabulous relationship. They love and care about each other, and he's pretty much her father in every way other than biology. People even comment on how she looks like him (not knowing he's not her father).
At this point she doesn't want a sibling - she did a few years ago, but has since decided they're noisy and irritating and thus doesn't want one. That said, she hasn't had much to do with babies so she may indeed enjoy them eventually.
I'm waffling, but basically... I'm just after advice and experiences of people who've had their child gain a sibling after ten or more years of being an only child...