I think it does not matter who received the payment. What the matter is "whether the money was dibursed from IRS due to the child being claimed." According to you a child's rebate can be claimed twice, one time when, for example, when mother claimed the child in 2019 return and then when grand mother claims the same child in her 2020 return by entering $500 on Line 6 and 600 on Line 9. If this is true the money is given out twice for the same child.

I am even more confused now. I call of the day.