There's nothing in the 628-page pandemic stimulus bill, known as the American Rescue Plan, that says a family's children must share the same father in order for parents to receive $1,400 per dependent.
The plan, which was signed into law by President Joe Biden on March 11, 2021, provides direct payments of $1,400 to most individuals making up to $75,000 a year. It includes an additional $1,400 per dependent.
Some users on social media apparently took a posted claim saying, "ALL the kids have to have the same Father to receive the $1,400!" as real, but all signs suggest it is satire.