I told my kids this weekend. They are 15 and 13, both boys. My 15 year old has two younger siblings from his Dad, so he's thrilled. He loves being a big brother to them, though he only gets to see them a couple of times a year.
My younger son is over the top excited. I was nervous telling him, considering he's "the baby", and I'm getting older and all that jazz. But he took so well to the news, and has been asking lots of questions about me, my health, what's going on, and interjects his thoughts on life with a baby and names, and things through out the day. I'm so thrilled. I had this vision of a wonderful relationship between these siblings BECAUSE of their years difference. That she wouldn't be the naggy/bratty/annoying younger sister (or brother), but more of a sweet little person to enjoy and be friends with.
I'm very happy for telling them.
Have you shared with the older siblings? Do you have experience BEING that older sibling?