If you're still interested, I have one that sort of fits your description:

Hounds of the Morrigan (http://hounds-morrigan.livejournal.com/tag/hounds+of+morrigan)

It's a pretty dark AU where Spock was given to Uhura when they were kids. Later on, they find an abused Jim, and include him in their family/team/relationship/whatever. They are all fairly messed up in this verse. One of the only threesome fics I've read and liked =)