What does Jonas’s father do when the identical twins are born?

The smaller twin is given an injection.... released.

"I am. I'm next on the list. 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."

Jonas' reaction....

He killed it! My father killed it! Jona s said to himself, stunned at what he was realizing. He continued to stare at the screen numbly.