This case is very similar to how adopted children often seek out their biological parents once they identify potential suspects.
I think based on Alex mothers ex husband negative DNA test and the arrangement made between her mother and Jethro which a relationship was established before Alex birth and after , I’d argue there’s definitely enough evidence to pursue this legal effort .
Im not sure why anyone would denounce in any way Alex intent to establish her biological father?
Besides the potential fallout from his wife Gene I actually believe since the skeleton is out of the closet it would be a very nobel gesture on Jethro to either admit he’s the father or take the test.