Parental control for xbox account

Hello. I am hoping for some help regarding my sons xbox account please.

I purchased my son a new xbox following breaking up with his father and set my son up a new account which I linked to a new Microsoft account that I created in order to do this. I had the account set so that I would receive a weekly report and that my son
had to request any purchases which I would then get an email to permit this, add money to his account and then he could buy skins and such for fortnite.

Last week my son asked me to alter something on his account settings and it was then that I found that his account was now listed as him being the user and my ex being the organizer. I was unable to gain access to alter any of the settings. Following this,
my son wanted to make a purchase but there was no longer an ask option, just a buy option. I instructed him to hit 'buy' wanting to see what would happen and sure enough, the purchase went through instantly and the money came out of my credit card.

I am now at a loss as to how to remove my ex from this account (which belongs to me) and reinstate myself as the rightful organizer. Any help would be greatly appreciated.

:)