I believe you are referring to more 2021 advance payments for having children. Did these people file their 2020 tax returns? 

The $1,400 alone would have been for a single person. If children were added in the 2020 return, there is now an extra $1,400 for each child.

https://www.irs.gov/newsroom/irs-begins-delivering-third-round-of-economic-impact-payments-to-americ...

Cash the checks. because everyone knows that IRS really has a handle on this!