My mum's partner of 15 years began doing this to younger women and other uninhibited things my mum wasn't at all keen on at 85! We were very concerned about his change of behaviour, and thought maybe he was starting with dementia, so had a word with his daughter. Her husband actually said "well you should forgive his little foibles, after all he hasn't raped you"!
Things became worse - in the end she wasn't sleeping, as he was up and down all night, doing heaven knows what, he stared playing 'mind games', such as hiding her rings and then finding them in a funny place and blaming it all on her etc. She then spotted him taking what looked like pills, and found an envelope in his car with kisses all over it addressed to him. Eventually she was so paranoid with no sleep, and so terrified of him that she went next door and her neighbour asked him to leave. Since she has come to live near me in the south, her neighbour keeps seeing him in the area, dressed as though he is trying to be incognito, staring at her old house. Had his daughter done the right thing and listened, and got him to the GP, she would have supported him, but it just became untenable. He was like my dad; my children saw him as their granddad - it was horrible, and we all miss the man that he was ... so sad.