You can use official apps for this:
Family Link for Parents — https://play.google.com/store/apps/details?id=com.google.android.apps.kids.familylink
Family Link for Kids — https://play.google.com/store/apps/details?id=com.google.android.apps.kids.familylinkhelper.
You need to create a family group, and all your family members will be shown here — https://families.google.com/families and here — https://play.google.com/store/account/family.
If you have troubles with some member’s account while trying to add them to the group saying something about different regions, you can use VPN on a device that needs to pretend to be somewhere else (I used this free one, as I needed 2 accounts to be in Russia — https://www.urban-vpn.com/locations/russia-vpn/).