Coran also has a substantial role in one of the sidequests in Baldur's Gate (if he's with you). If you elect to partake in the Brielbara quest, and if Coran is in your party, you'll find out that Coran is her daughter's true father and she'll pester him about it. He in turn decides he must do something about the curse placed upon her by Yago, and will ask you and the rest of the party for help in doing so. Now, I've never turned him down, so I don't know if he'll get mad and storm off, but I'd imagin so, everyone else with a subquest does. ~_- Once you find Yago and take his book of curses back to Brielbara, she'll pester Coran some more about whether or not he's ready for the responsibilities of fatherhood. She'll wander off after his uncertainty about the matter and will remain in your party.

On a personal note, Coran is one of my favorite characters in the game. He's great with a bow, and he's a good thief. If you want to have a little fun, get him and Safana in the same party and they'll banter back and forth. ~_-