Is it better to buy two cavalier king Charles spaniels or one?

2

Because when nobody's in the house they will have someone to play with I have 2 and they are brother and sister. But only if they come from the same litter. You should only buy one at first to see if you can manage before getting another one. A second one might also cause fights and aggresive behavior, but if trained correctly, they will get along fine, as long as they are not bought at the same time