Lovely intelligent breed - no surprise that Queen is in love with this breed. Moreover it has very different body shape, I had a good task to create pattern that would let me produce comfortable corgie raincoats. Oh dear, their stomach is so close to ground that you cant add any extra looseness that is not necessary. Who's got corgie and had no outfit problems?
They are at least somewhat related. I read that the two breeds were only considered separate breeds from the 1930s on ( I could be wrong on the date). Both come from different working dogs that were each likely crossed with a dachshund to get the short legs. The Pembroke has a finer pointier face and so there is likely a spitz type of dog (German) in their background. The Cardigan maybe has some other slightly sturdier farm or working dog (Nordic) in his lineage, mixed with the dachshund for the short legs. Originally the Pembroke was bred using the Cardigans I read, so if that is true they are super related! Their temperaments are slightly different but they have the same health issues which may be another clue. Both are great breeds.