Diasoman

The Diasomans are a humanoid race with yellow skin, gold eyes and pink hair who hail from the planet Diaso II. They are most notable for always coming in pairs - every Diasoman has a twin, with whom they share a strong bond, to the point that these pairs are usually addressed by a single name formed by combining the twins' individual names.

During her early years at Starfleet Academy, Kathryn Janeway shared a room with a Diasoman pair, collectively called Thrum'Pol. She compared their arguments to the sound that one might hear listening to two toothless cats trying to argue underwater with each other in German. (VOY novel: Lifeline)