2 Stimulus payments sent for same kids based on different tax years

If duplicate payments for the 3rd stimulus are sent does one recipient need to pay it back? Folks claimed my kids on their 2019 taxes (we lived with them), I claimed them on my 2020 taxes. They got both stimulus payments in 2020 and I got a rebate credit on this years tax returns. I received the 3rd stimulus payment today but my folks also received a payment for my kids. They haven't filed 2020 taxes yet, so it was based on 2019. So do they need to return this most recent stimulus payment? Or the previous ones?