"Multiple definition of 'gridLayout'"

[jacek]

I originally made it in Designer, compiled the .ui file and then just took the parts I needed for Ui_PokerInfoTable.h and put them in the PokerTableInfo class

These variables are global, they don't belong to any class.

so that I didn't have to let it inherit Ui_PokerInfoTable

You don't have to inherit from Ui:xxx classes to use them. You can use aggregation instead. With your approach you have lost possibility to change the layout with Designer.

It works fine if I change the name of the gridLayout variable to gridLayout1.

That's because you never use those variables.