Concur, came to the comments to say the same.
…or a really quick and awkward way to bring an end to the strip.
Just because they are not identical, does not preclude them being twins. If they came from the same litter they would still be fraternal twins. However, since most puppy litters are closer to six, they are more than likely sextuplets.
Concur, came to the comments to say the same.