[The Penguin]

by that I mean they stick together as one and tend not to form close bonds with other people because they are so close to eachother and any friendships they have can't compete with the relationship they have with eachother
that is less true for normal brothers or sisters because the bond isn't as strong and enduring as it is for twins
normal siblings might drift apart after the leave home whereas twins stick together
that could explain partially why Karissa and Kristina are the way they are in the house

[spintronic]

Originally Posted by The Penguin

are twins in general sort of isolationist?

I could think of better ways, like placing them in a box & burying it at the North Pole.

Then I'd say they were "ice-olationists".