I haven't read them recently, but I did see the BBC versions recently. Caspian marries a girl they meet on the last island before Aslan's country in Voyage of the Dawn Treader. She's the daughter of a star. Caspian is a background character in Silver Chair. He's going to journey to all the islands again at the beginning and conveniently is back in his castle in Narnia when Eustace and Jill bring his son with them.

It really kinda depends when you're setting this drabble: circa Caspian book, or Voyage or SIlver Chair.

OH! I can't remember if this happened in the books, but in the BBC film versions (which are pretty book acurate), when Caspian dies, Alsan returns him to the age he was in Prince Caspian (very much younger than in the movie that just came out) and allows him to visit the Summer Country aka our world. It's not for very long and Caspian helps Eustace and Jill fight off some bullies...

Hope this helps