Ideally two sisters that will play and get along with each other.
As others have said, this is a perfect example of things you can't control. I have had many csts in my life, including siblings that got along well, siblings that hated each other, different strays that got along super well and other that just could stand each other.
And a lot of support, especially aimed to the beginner userbase. Most basics questions a first time linux user will encounter are usually answered to by searching the forum