According to the authorities, the boys had been receiving hospice care at their home in Pennsylvania, north of Pittsburgh, before they died on Tuesday.
Andrew and Garrett Stancombe were born on April 10 to Michelle Van Horne and Kody Stancombe who already have a 22-month-old son together.
The couple decided against risking surgery to separate the boys, Andrew and Garrett.
The boys' funeral is set for today evening.