"radio123" wrote in message ...
Can my father use my GMRS license to communicate with my sister?

Question...Does your sister WANT to communicate with your father?

What if
I don't go on the vacation can they still use my license? Does the license
cover the whole family where ever they are in the USA and even if I am not
part of the direct communication ?

You will find that the FCC considers "family" to be the residents
of the same household. If by "family" you mean anyone in your DNA
chain regardless of where they live, you'd find the FCC would frown on
that, regardless of whether you were on vacation or not.

One license per family ?

Same household...Not everyone in the same DNA strain.

Steve, K4YZ