One of the main reasons I have gotten into this is because after seeing the benefits of one card (SPG) and some free nights on a trip last summer, I realized that my (now) fiancé and I could have a pretty great destination wedding and honeymoon in +/- 2 yrs time.
That said, it would be an even better trip if I could convince some family members to also join the game and the entire family could join us for the destination wedding, without having to complain about their cost for airfare. But, like everyone else has said, the chance of convincing an entire family to go along with that is slim. I don't want to think about the faces I would see explaining this to everyone. I won't even start to consider what would happen if I tried to tell different people to join different programs to avoid diluting the awards pool so we can all get there for less . . .