If claim my Son as a dependent can I also claim my daughter in law and grandchild?

My son is married and has a son; he earned very little in 2020, I paid for almost all of his and his families expenses.  He submitted a joint return and claimed his wife and son as dependents,  Since he made less than $4,300 I know that I can claim a Tax Credit for him as an Other Dependent but can I also claim his wife and son as Other Dependents?