how can i remove a minor from family sharing

A minor as in a minor child?

If so, you cannot directly remove them from a family group, as Apple IDs for children cannot exist outside of Family Sharing. You can move them to another Family Sharing Group. see: link-> Move a child to another group using Family Sharing - Apple Support

If you need to completely remove the Apple ID for the child, then you need to contact Apple Support to have it completely deleted. See: link-> Contact Apple Support for Apple ID account issues - Apple Support

If the age was set to under 13, you need to contact Apple support to fix it as well. Children IDs are very limited.

If it was set to over 13, you can log in to the Apple ID on https://appleid.apple.com and change it there.