Write to the Chinese government and ask them to ensure that children are allowed to leave China to be reunited as promptly as possible with their parents and siblings already living abroad, if that is preferred by them.

Template letter:

Dear President Xi,
I am alarmed to learn of the reports that some Uyghur parents have been separated from their children for years as a result of the unprecedented crackdown on ethnic populations in Xinjiang.
Since 2017, an estimated one million or more people have been arbitrarily detained in “transformation-through-education” or “vocational training” centres in Xinjiang, where they have been subjected to various forms of torture and ill-treatment, including political indoctrination and forced cultural assimilation. This mass detention campaign combined with systematic repression have prevented Uyghur parents from returning to China to take care of their children themselves and made it nearly impossible for their children to leave China to reunite with them abroad. Some Uyghur parents believe their children may have been taken to state-run “orphan camps” or boarding schools when the relatives taking care of them were detained.
I therefore call on you to ensure that children are allowed to leave China to be reunited as promptly as possible with their parents, if that is preferred by them, as well as with siblings already living abroad.
Yours sincerely,