Star Trek: 10 Alien Species That Are Actually Related

In the Deep Space Nine episode The Alternate, the scientist who raised Odo, Dr. Mora, came to the station to tell Odo that a lifesign was detected on a Gamma Quadrant planet that looked very similar to his own. Odo, still unsure of where he came from, went to the planet with Mora and a small team to investigate.

On the planet, L-S VI, they found a strange monolith that they identified as a relic of Odo's people. Evidently, they were correct, because a nearly identical monolith could be seen when they eventually visited the Changelings' planet in The Search.

There were no Changelings left on the world, suggesting that the planet was abandoned after they went into hiding, but a small Changeling-like creature remained. This creature also had the ability to shapeshift, changing shape every time that it reproduced, and it shared much of the same DNA with Odo. Dr. Mora said that they could be 'distant cousins'. Unfortunately, the creature died shortly after being taken to the station because there wasn't enough carbon dioxide in the air, so we never got to learn more about this mysterious offshoot of the Changelings.