The Social System:
Whatever your station or birth, the three most important things in every persons' lives were kinship, social status and religion. Everyone needs food, shelter and companionship, though many deprive themselves of these for religious ends and thousands of peasants accept that they will starve to death each year. But once these simple needs are satisfied all must consider where they stand in relation to their kinfolk, their "betters" and "those beneath them" and most importantly of all, where they might stand when they come before God at judgment day... So, whatever else goes on your character sheet, have at least a brief answer to questions about these pillars of medieval identity. Still, there are those that Choose not to conform.
But first the caveat (or the first rule for looking at social interactions):
Lots of things might potentially count or be important to the matter at hand, what in fact is important only becomes "certain" (ie it's a "made up" thing) after the matter is resolved. Before that it is a kind of game or power play (often involving force) to see which elements count. After that, most involved have a stake (for one reason or another) in at least publicly accepting a version of events that legitimates what took place.... So just as there is no actual calculus to determine how kinship, social status and religion should be weighted in relation to one another, it's actually up in the air how, for instance, a legitimate female cousin's rights should be weighed against a much loved and useful bastard son. The three elements matter, how exactly they matter in any one case is open to contest.
The caveat needs to be considered in light of the "zeroeth" rule for looking at social interactions, watch what the do, not what they say about it.The Caveat cuts both ways, when trying to influence individuals, you should work to maximise uncertainty (say by giving them some reason to believe that others, possibly their superiors or kin, may take an interest in what happens) to create opportunities for outcomes which that individual might not have otherwise countenanced. then it's just strategy, try and make considerations that favour you matter the most in the interaction.