With a bit of trickery, this can be done. See the invisible tab control in this demo file:
Note, however, that if you used a visible tab control with tabs labeled Parent and Child, you can get much the same result without needing any extra tricks to make it happen.
That worked, now another question :), I have both radio buttons as seperate buttons, not as one. How can I make it to where if i select one of them, i wont be able to select the other one?
Simplest would be to use a single field with a two value value list instead of separate radio buttons.
Otherwise, you can use button set up to perform script when the field is clicked:
Set Field [Yourtable::Parent ; "valuefromParentvaluelist" ]
Set Field [YoruTable::Child ; "" ]