I did have two kittens from the same litter - Hamish and Fergus, my Glaswegian cats, now long departed, and they loved each other to bits, Sure, there was fur flying from the behind the sofa sometimes but they did what cats are expected to do, shared their bed, and so on - Hamish really missed Fergie when he died, but sadly he died the same weekend a year later - and when Hamish was the only cat, he came out of himself, he'd always been the background cat of the two before. Fond memories!