What benefits did your aunt retain once she gave you the house? Was it just using it as a holiday home?
There seems to be an important fact that YOU allowed him to live there and she had to ask your permission, rather than your aunt offering it to him as 'her share' of whatever benefits she was retaining.
It isn't 'a house your aunt bought in your name' - she bought you or gave you a house.
It isn't 'technically' your house - it's your house.
The whys and wherefores as to how it was bought are irrelevant.
It's a truly horrible situation OP, and a shocking reminder as to just how badly people behave once someone has died.
Not just nasty freeloading grifters like him, but family men, the men who will inherit everything in a mirror will 'but can be trusted to pass everything on to the kids'. Oh no he can't. I could tell you some absolute horror stories of lovely husbands, great Dads, who let a deceased wife's assets slide into a new woman's grasp and then on to her own kids. They don't mean to be like this...but it happens, Again and again. People need to be so watertight in the way things are set up.
Good luck with all this OP, so disheartening.