I have English Toy Spaniels. I’m not sure if what you are referring to as cloven/joined pads are the same as what we refer to as fused toes in our breed. It is not considered a fault or a deformity, but a trait of our breed. I’ve also been curious if there are other breeds with this trait.

Of the 4 English Toy Spaniesl I’ve had, 2 have had fused toes. They are not always on all feet. The dog in this photo has fused toes on 3 of his 4 feet - but not all toes are fused, and those that are fused are not fused in the same way.