Are your twins antisocial because they have each other?

[twowhat?]

The multiples forum has been dead for so long. But this weekend I really started to wonder about this. My girls don't play easily with other kids. Is it because they always have each other as a "safety net" playmate to fall back on? This weekend they even backed each other up...DD2 was wearing a princess dress that another little girl wanted to wear, and the other girl told DD2 "I want to wear that dress". DD2 (who simply doesn't stand up for herself) was on the verge of tears until DD1 walked up to her and whispered in her ear, after which DD2 told the other little girl "No, thank you" (as in "No thanks, I'm not going to let you wear it). It was very sweet but at the same time...this is gonna make it really rough on my girls when they split them up in public K (next year), right? What can I do to help prepare them? DD2 is especially dependent on DD1. I wonder if I should go ahead and tell them that when they go to "big Kindergarten" they will not be in the same class...but my kids are sensitive and anxious to begin with and that might just cause unnecessary stress and worry.