My uncle finally admitted it a couple of years ago when he was arrested for harming his wife. He had dodged out of the way when she lunged at him. She fell and broke her arm. Their eldest son (who was also a wife batterer) reported him to the police. When he was being questioned at the police station he broke down, told them everything and showed them the scars from when she stabbed him, scalded him with boiling water and burned him. The police officers believed him and one told him that he too had been a victim of domestic abuse at the hands of his wife so understood how hard it was to talk about it.
They gave him an emergency contact number and told him to phone them whenever he was attacked. He did so at first but then decided he was wasting their time. His wife still lives with him. Now she reckons she's ill but she can still move fast enough to hit him or throw things at him. She also uses her illness to make his life even more miserable. He's a very fastidious, tidy man. She refuses to wash unless she's going out (he has to drive her), eats in her bed staining the sheets and leaving rubbish everywhere, phones him constantly if he goes out and, if he stays out for too long (in her opinion), she smashes up the house.
We tell him to leave her but he won't. He says he married her for better or worse til death they do part. He's in his seventies and sadly I think that's what will happen. I know this is horrible but I hope she goes first so at least he gets a few years of peace before his time comes.