This is just an observation that I have recently made. I had a pair of cats that were brother and sister (different litters - same mother). They always behaved like a "couple". They were generally inseperable, except when they had a fight, and then they would sleep in separate rooms. A fight for them was very rarely loud or aggressive, they just seemed to have a difference of opinion (about a toy, or sleeping place).
Now I have two cats that are not brother and sister. These two act like they are brother and sister! They are generally in separate rooms, with two notable exceptions. First, they both really like to be in the same room that I am in, so they will occasionally lie in different parts of one room if I am there. Second, they both appear if there is something of mutual interest, like feeding time, a strange noise, a bird near the window. They growl over everything with each other, from toys, to food, to litter boxes.
So, that is my observation of the strange - the pair that WERE brother and sister were so close that they behaved like a couple and the pair that were NOT RELATED behave like brother and sister.
Now I have two cats that are not brother and sister. These two act like they are brother and sister! They are generally in separate rooms, with two notable exceptions. First, they both really like to be in the same room that I am in, so they will occasionally lie in different parts of one room if I am there. Second, they both appear if there is something of mutual interest, like feeding time, a strange noise, a bird near the window. They growl over everything with each other, from toys, to food, to litter boxes.
So, that is my observation of the strange - the pair that WERE brother and sister were so close that they behaved like a couple and the pair that were NOT RELATED behave like brother and sister.
Well, after she grew up a little. 
Once she was out of quarantine, healthy and more grown up...well, she's the only girl Trent will play with. He likes her and is pretty protective of her. She's not the snuggling type, which works good for both of them.
