If you mean between NPCs, I sincerely hope so. I don't know how hard that would be to implement however (I mean having a relationship develop between NPCs, completely independent of the PC), although I'd still find it funny if one person kept coming on to another and constantly got shot down.
As for between the PC and NPCs, the idea of maybe flirting to get extra information (slightly like the speech checks in Fallout after certain perks, though not completely the same) could be good. I don't think it should go further than that, although I'm aware others disagree.