A karass of only two people, who are so bound together that even their children cannot invade their union. From Kurt Vonnegut's "Cat's Cradle." (A karass is a group of people bound together, often without externally discernable ties.)
From "Cat's Cradle":

“They were lovebirds. They entertained each other endlessly with little gifts: sights worth seeing out the plane window, amusing or instructive bits from things they read, random recollections of times gone by. They were, I think, a flawless example of what Bokonon calls a duprass, which is a karass composed of only two persons.”
by Kurtzi March 16, 2016
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An karass consisting of only two people.
My parents have evolved into a duprass; no one else matters.
by Frabanoogle January 30, 2016
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