This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

n. A person who conjoins

"The addition of Heroes like Galiana and Clavain and Felka pervert that ideal slightly, but in later centuries there are more post-human conjoiner models, and their society loses it's openness by the creation of secret councils and the antagonist Skade emerges."

conjoined