You have to also count in your support the cost of the house and utilities and everything. So you might not provide over half of your own support. If they try to claim you as a dependent then their efile will reject and they will have to mail their return. If you can be claimed as a dependent you will have to amend your return.
How to amend a 2020 return
https://ttlc.intuit.com/community/amending/help/how-do-i-amend-my-return/01/27439
