The Kaveetch were the original natives of Sontar that created the Sontarans. They were natural-born members of their species and, unlike their creations, did not use mass cloning techniques.
They also considered themselves to be the real "Sontarans" (in parallel to humans being "Earthlings"), and preferred not to refer to the clone race commonly known as the Sontarans as such, using the name "Sontaran clones" instead. (AUDIO: The First Sontarans)
Biology
Unlike the Sontaran clones, the Kaveetch reproduced naturally. They appeared more like humans. (AUDIO: The First Sontarans)
History
At some point in their history, the Rutans attacked Sontar and it started a war between the Rutans and the Kaveetch. The Kaveetch were losing the war so they began to clone themselves to replenish the soldiers they lost. The clones eventually became the Sontarans and the Kaveetch were forced to leave Sontar.
A group of Kaveetch, including Meredid Roath, the creator of the Sontaran clones, used their time travel technology to arrive at 19th century Earth, where they were being pursued by the clones and were forced to enter into a makeshift alliance with the Rutans. They were assisted by the Sixth Doctor and Peri Brown, who helped them relocate to a different planet. (AUDIO: The First Sontarans)
Anura knew the Kaveetch. (AUDIO: Truth and Bone)
Legacy
According to Strax, it was impolite to speak of the Kaveetch and their similarity to humans.
Vastra threatened to revert Skark's Sontarans back into Kaveetch, causing them to flee London. (AUDIO: Truth and Bone)