Stingr69
Papillon Fan
Coton Du Tulear? One of the trainers at the local club has one. OMG it brings a smile or a tear to everyone in the audience at the performance. Not a spaniel I know but what an amazing animal. 

These dog breeds are closest to a cavalier, simply because they come from the same type, spaniel.
American Water Spaniel
Boykin Spaniel
Clumber Spaniel
Cocker Spaniel
English Springer Spaniel
English Cocker Spaniel
English Toy Spaniel
Field Spaniel
Irish Water Spaniel
Sussex Spaniel
Tibetan Spaniel
Welsh Springer Spaniel
French Spaniel
Ime English cockers are pretty darn close. Papillons ime tend to be sharper than cavs .
These dog breeds are closest to a cavalier, simply because they come from the same type, spaniel.
American Water Spaniel
Boykin Spaniel
Clumber Spaniel
Cocker Spaniel
English Springer Spaniel
English Cocker Spaniel
English Toy Spaniel
Field Spaniel
Irish Water Spaniel
Sussex Spaniel
Tibetan Spaniel
Welsh Springer Spaniel
French Spaniel
Tibetan spaniels are not actually spaniels - they are related to Asian breeds like pekes and shih tzu
As far as the others go, there is quite a variety in temperament among spaniels when you go from companion bred types (like Cavs and American cockers) to the dogs bred for hunting. A boykin is going to be very different to live with vs a cav, though the sweet spaniel temperament will be there.
I think out of the spaniels, a pet/show bred English cocker would be pretty similar in temperament to a Cav.
For non-spaniels, I agree with the coton and havanese. What about a lhasa apso? The ones I've met were super sweet, mellow, and velcro little dogs.
Coming from a groomer's perspective....Cavs are super sweet. Lhasas and Shih Tzu's can be little demons. For what that's worth. :lol-sign: The Lhasas I've met have all offered to bite (and/or bark/charge) in one instance or another, even the "sweet" ones that I liked.