Arnold Perry admitted two felony rape charges and a sexual battery charge in court in Ohio in the United States.
The court in Mahoning County was told how the 34-year-old had befriended the girls' family after their mother had let him move in after he had nowhere to live.
But he abused their trust and raped the girls in 2015 and in 2016 in the small US city of Youngstown.
All three girls became pregnant, and one of the 14-year-old twins had an abortion soon after it was discovered, but the other two girls had to continue the pregnancies as they were too far along when it was discovered.
The Vindicator reports that Perry has been jailed for 27 years for his crimes.