hey guys

i must say this fork thing is mighty confusing for me. even tough i am following BTC for a while.
please forget my ignorant questions but i am really lost with this topic and i don't want to loose my hard earned BTC.

2 questions:
- i keep the majority of my BTC on my trezor wallet. do i need to do anything in case BTC forks?
- additionally, my my parents bought some BTC because i am told them too invest a little bit and they keep it in a armory wallet. do they need to do anything?

last question: some people in other threads mentioned that one could double their BTC if they switch to XT. is that correct? and if yes, is this doubling only for the people that switch at the beginning and people that don't switch immediately loose out on this opportunity? or will the amount of BTC double when the majority decide to fork? if i/we need to do something, how can someone using trezor and/or armory make this happend?

again, sorry for those questions. but i am neither a mathematician nor a programmer so some of the more technical aspects of BTC are to confusing for me..