- Additionally in the Burning Basement.
Gemini starts as a pair of bosses connected together by an umbilical cord.
- Contusion chases Isaac and periodically charges increasing his speed, but stops to catch his breath afterwards.
- Suture, while attached to Contusion, shoots a projectile towards Isaac if not behind an obstacle.
- If Contusion is killed, Suture detaches and begins charging furiously at Isaac. He has high momentum and takes extra knock-back from tears which can cause him to gain speed.
- If Suture is killed, there is no change to Contusion's behavior.
Champion Versions 
- Cyan: No difference in behavior. However, Contusion will drop a Soul Heart if killed last.
- Green: They start separated from each other and have no difference in behavior.
Gemini as one of Delirium's forms.
Contusion in-game prior to Repentance.
Gemini as one of Delirium's forms prior to Repentance.
When fighting Gemini, the following obstacles can spawn:
- Rocks in 4 different combinations
- Rocks will always appear when fighting Gemini.
- Gemini appeared in the original The Binding of Isaac.
- Gemini seems to be an example of a parasitic twin, with Suture being the underdeveloped twin, dependent on Contusion.
- Blighted Ovum is the posthumous version of them, and Steven is the alternate version.
- The Gemini pair is named after the astrological sign of the same name; the symbol of Gemini is a pair of twins.
- The Gemini pair was originally designed to be a boss in Gish and was called Suture Contusion, with the larger twin being Contusion for the boot-shaped dent in his head.
- Contusion is the medical name for a bruise, whereas suture is the medical name for a thread used to close gaping wounds, commonly called stitches.
- The names of the brothers are inspired by a song by The Mars Volta
- The specific lyric comes from "Cicatriz ESP."
- In the Bestiary, Suture is referred to as "Gemini Baby".
|Bug!||For The Cellar to unlock, the player must kill all the Basement bosses once. Gemini, however, counts as two depending on which part is killed first.|
|Bug!||If you Stun Suture at the same time that it tries to shoot Isaac, it will cause the sound effect to loop infinitely until Suture is killed.|
|Bug!||If Gemini's chain hits Red Poop or Spikes, the chain will disappear but Contusion and Suture will still be joined.|
|The Binding of Isaac: Rebirth|
|Achievements||Attributes||Bosses||Cards and Runes||Challenges||Chapters|