Twins are a pair of children that are born from the same pregnancy. Some gods, Titans, demigods, and mortals are twins. They don't need to, necessarily, look alike as there are two types of twins - identical or fraternal.
Twins in the series
Titans
- Prometheus & Epimetheus
- Helios/Sol & Selene/Luna
Gods
- Apollo/Phoebus Apollo & Artemis/Diana: They were known as Letoides, meaning the children of Leto.
- Ares/Mars & Enyo/Bellona
- Hypnos/Somnus & Thanatos/Letus
- Deimos/Metus & Phobos/Timor
- Pegasus & Chrysaor
- Zethes & Calais (Boreads)
- Boreas/Aquilon, Notus/Auster, Zephyros/Favonius, & Eurus/Vulturnus: Wind Gods (quadruplets)
- Calliope, Clio, Melpomene, Erato, Euterpe, Polymnia, Terpsichore, Thalia, and Ourania: Muses (nonuplets)
- Frey & Freya
- Balder & Hod
Demigods
- Castor & Pollux
- Zethes & Calais (born demigods, became immortal)
- Romulus & Remus
- Holly & Laurel Victor
- Jun'ajpu' & Xb'alamkej