Can I contribute $6000/year in my kids Roth IRA, provided they don't have earned income?

Hi,

I've two school going kids age 5 and 11, both are non-US citizens and have ITINs.

I recently opened Roth-ira for them and would like to understand if I can contribute $6000 from my after-tax income every year for each one of them?

Do they need to have any income in the year to contribute to Roth IRA or they are good if 100% contribution every year is done by me (father) itself?

Thanks in advance.