Wiktionary
n. 1 (context uncountable English) The condition of being a twin 2 (context countable nautical English) Either of a pair of ships of exactly the same design
Usage examples of "twinship".
In nightmare after nightmare, Bedenbaugh would blend with his father in a terrible twinship and their mutual screams would teach the sleeping priest again and again about the penalties of fire.
Would we ever know that there is a relation of twinship or rivalry between a man and his planet, if there were no sign upon his body or among the wrinkles on his face that he is an emulator of Mars or akin to Saturn?
Sweat and scratching had altered his twinship with Al Jolson to a mildewed, albino-tiger look.
Apart from their name and their twinship, they were in no way outstanding and certainly had not, so far as was known, any enemies.