It's kind of hard to say, as I don't know how you are picking.
For example if you just say
family move to x
all objects in that family will move to x
or if you say on collision with family
It will pick only the object that have that particular collision.
So if you were to compare a pv in a family all objects with that pv will be picked, but if you were to do something like
family set pv to 1 all objects with that pv would set the pv to 1... unless you have an additional condition that tells it otherwise.
Now it is possible to put objects with different pv names into a family, but that wasn't always possible to do that. You might want to check out all the pvs in the family editor, and if some are missing you may have to add them manually.
Supposedly every object in a famly should share all behaviors, as well as pv names.