Our cat just turned a year old this month, and a few months ago we had issues with her companion being extremely aggressive towards my 4 year old, so we decided it would be best to rehome her.
Unfortunately we can tell our remaining cat is lonely, we play with her and give her as much attention as she will allow (she is very aloof, won't stay in anyone's lap, is not a cuddly cat at all and prefers attention on her terms), but it's not enough. She goes through our house meowing and howling, and is restless.
I'm curious though if she could get along with a dog. After our experience with the cats, I'm a little wary of bringing in another cat, the two we had had a LOT of behavior issues, although rehoming the aggressive one seems to have calmed down the resident cat quite a bit, she still has things she does that can be quite frustrating, which we work on every day (and I do think some of it is because she's lonely).
She's a purebred Bengal, and I swear sometimes she's more like a dog than a cat, although I do know she's still a cat, so that's why I wonder if she would get along with a dog and not be lonely. I don't want to get a dog and then find out we just made the problem worse.
She was initially raised around several dogs at the breeder's house, and she was about 4 months old when we picked her up, but we do not have a dog ourselves now, so I don't know if that will have an impact or not.