Twins are not allowed because having two identical people walking around would be confusing. The babies are weighed as soon as they are born, and the lighter one is euthanized (“released”).
In The Giver, everything is tightly controlled. The Community is ruled by a concept named Sameness, which basically means that everyone is the same. Choices are made for people. The goal is to ensure that no one is uncomfortable. For a person to be uncomfortable is a terrible thing in the community.
"Well, they can't have two identical people around! Think how confusing it would be!" Jonas chuckled. (ch 19, p. 146).
The smaller twin is released, which means that it is euthanized by lethal injection.
I'll have to select the one to be nurtured, and the one to be released. It's usually not hard, though. Usually it's just a matter of birthweight. We release the smaller of the two." (ch 15, p. 114)
When Jonas finds out what release really means, he is horrified. He cannot believe his father would kill an innocent newborn. As a result, he decides to leave the community, returning the memories to the people and ending sameness.
Lowry, Lois (1993-04-26). The Giver (Newbery Medal Book). Houghton Mifflin Harcourt. Kindle Edition.
Correction to the other person whop answered-- But this is a dytopian society-- a place where people would fear to live in-- theres a dictator,they think violence is necesasary, tech sometimes replaces humanity, nature is usually destroyed
The Giver is about a utopian society. A utopian society is known as a "perfect world" or a "perfect existence" If there are two babies with the same DNA, the society would not be perfect-there would be a flaw. It would show that science has yet to fix that "inaccuracy" and it takes away from the other twin's reason for existing. When the baby is born, there must be no flaws, no birthmarks, no slow learning processes-or they will be killed. I hope I have helped you!