From Critical Hits:

I put a lot of effort into my characters. I wanted a really classic feel to my adventure, so I used races and classes that have been ubiquitous across Dungeons and Dragons settings over the years. Instead of trying to come up with “neat” character concepts, I spent time trying to have the characters feel more real, choosing character powers to match their personalities as well as their relationships to the other party members. For example, a husband, his wife, and her brother made up half the party. Both the husband and the brother had powers that worked well with the wife/sister in combat, but not so well with each other – I wanted to stress the jealousy between the two. The eladrin wizard was written to often feel like an outsider to the rest of the party, so his powers did not rely heavily on the actions of the other heroes.

Having the powers reflect the relationships is really nifty.  I remember making my 4e Rogue with a touch of Warlock who was the Grey Mouser to Storn’s Fafhrd and when our powers synced up it made for fun-as-hell high five moments.