Player > Feats > Intuit Relationships
You can quickly sense relationships between others and use that knowledge to manipulate them.
Perception 1 rank, Sense Motive 1 rank.
After 1 minute or more of interaction with or observation of two or more creatures, you can attempt a Sense Motive check to intuit the relationship between or among those creatures. If you don’t understand the language they are speaking, you take a –5 penalty to the check. The DC is equal to 10 + the highest Bluff skill bonus among the creatures or 15 + 1-1/2 × the highest CR among the creatures, whichever is higher. If you succeed at this check by 5 or more, for the next hour, you gain a +2 circumstance bonus to Bluff, Diplomacy, and Intimidate checks against the creatures when you use their relationship as part of the interaction. The GM decides if the bonus applies. If you fail the check, you can’t attempt to use this benefit on the same creatures again until you gain another rank in Sense Motive.