If you want the entire family's variable to change you will have to create an event that does that. You can change an entire family's variables at once by performing the "Set value" action on the family instead of each object within it.
To set up variables for whole families at one time in the Layout editor you can use the Manage Families button at the top located under Project.
And of course, you could always have your family set it's variables to those of a specific object within that family by using events. So if "objA" is in the Blue family, you could do this:
-> Blue: Set 'myVar1' to objA.Value('myVar1')
-> Blue: Set 'myVar2' to objA.Value('myVar2')