Co worker married and fancys me 🙁

OK so I have a coworker who is 65 he is double my age from day one has been one of my biggest supporters always got on with him and I like his work ethic,his a positive person funny and at work he is probably the only person who supports me in my work place. In short I work in leisure and want to be a pt, however he is married and he jokes about me being his favorite the jokes are getting a bit too far though he jokes about wearing me down, and has joked about me sleeping with him, things have got really weird at first I thought he was just good supportive colleague but my gut says his gone too far. I’d never ever mess with a married man if I’m honest if he was 25 years younger and not married I probably would be tempted but I’m definetly not, I enjoy and like his support as a friend but I feel like I can’t be his friend anymore because he jokes about sleeping with me. I really feel for his wife who has been Married to him since they were in their late teens maybe it’s a male ego thing?? I have actually thought about moving my job because it’s getting awkward I’ve told him straight I do t mess with married men he hasn’t taken the hint 😐