There is no rule of any kind prohibiting ANYONE in the audience from eligibility unless they have been called before.
While I follow the same reasoning as Chris that you'll stand a better shot of getting picked FROM a group, if you were to all split up, so be it. There are many times that friends, relatives, and other group members have returned on later shows and been called down.
Those who remember Michael Marlow (Buy or Sell), you could take notice a few weeks after he was on the show, he returned to the audience, and his aquantance won a car playing Any Number.
The last time I flew to LA, my flight attendant played 5 Price Tags in 1974! Her son was a contestant in 2002. Her daughter in 2003.
Again, there's no rule about having people from the same group being chosen. The Producers enjoy picking a cross section from the audience, but you will most often see group members get chosen rather than not. I have however, seen shows where there were a minimum of 5 groups, and only 1 had a contestant chosen.
Like it or not, the personality and smile is what's gonna get you to the row. So split up, stick together, do backflips...just be sure to have a good time in that interview!