He should get the Stimulus amount for the 10 year old again even if you got it in 2019. So something is wrong on his return. The 10year old must not be showing up as a dependent on his return. Delete the child and re enter him. Go slow and watch the questions.
For your return, sorry. The Recovery Rebate Credit is based on the number of people, not which one. You already got the stimulus for one child last year. And you are only claiming 1 child this year. But he gets the amount for the 10 y/o this year. So together you are getting the 10y/o amount twice, which is the same as claiming 2 children.
