Hello, thank you for reaching out to Microsoft Q&A.
According to the Microsoft article here, only the user with the Organizer role can remove family members or child accounts from the Family Safety group.

Reference:
How to leave a Microsoft family group
If you no longer have access to the Organizer account, use the account recovery form to recover the account.
https://account.live.com/acsr
Remember to use a familiar device from which you've frequently accessed your Microsoft account, as well as a familiar location. Microsoft will review your responses and respond within 24 hours. If you are verified, instructions on how to log back into your account will be sent to you, and if you are not verified, you will need to submit the Account Recovery form again. You can do this up to 2 times every 24 hours.
Please note that Microsoft Support cannot remove your account from the family group; you will be redirected to the Account Recovery pages linked above.