Then I must assume you are in conflict with this ex and you do not trust that the income for the bookings will be sent to you ?
If so, it is a tough one ! and I am afraid I do not have any immediate solution for you.
As a co-host, do you have full access to the account ? If so, you can remove the payout method that routes the funds into the account of your ex. There is also the option to remove the account and cancel the reservations, then set up a new account on your own.
I would try and contact airbnb with the issue - there is a chance they can help.