If I delete my iMessages, will they still be seen in iCloud?

My dad is the administrator of my family's shared iCloud account (he has the entire family using the same Apple ID and the same iCloud account on our iPhones). Because of this, I know he has access to my iMessages.

My question is: if I delete my iMessages, will they be removed from iCloud, meaning will he be able to see the iMessages after I delete them?

I would guess that they would also be removed from iCloud, but I'm not sure. If you can try it and then check the Messages app on his phone (or another in your family), you should be able to find out.