Married, wants out but hard cause of his young kids

Before anyone comes at me sideways, I would really like some positive advice although I know it sounds pretty shitty. Long story short, a guy at my work and me recently became friends, beforehand, we never spoke to each other. Turns out we both had eyes for each other. Of course I knew he was married so I didn’t act on anything, to myself I thought he was attractive and he felt the same but again, we never acted on it. We both didn’t know we felt the same until 2 weeks ago. He did tell me he’s unhappy in his marriage due to his wife cheating twice on him and hasn’t been able to forget or move on from it since it’s always in the back of his mind. He told me he’s thought about leaving her numerous times but he is worried about his kids as they are still young. He doesn’t want to be selfish to leave and break their hearts. He said even just the thought of it hurts and scares him like hell. I understand where he’s coming from and I don’t blame him but at the same time I see so many unhappy people in marriages and only to stay cause of kids. I don’t always agree that’s the answer because kids eventually see things. He said he wants to be happy and that even though it’s wrong he has semi feelings for me, he’s been an emotional wreck because he doesn’t know what to do. I wish I could give him advice but I can’t because he has his children to think about as they come first. All I said is I know he has a lot of regrets in his life I don’t want him to regret anything more later down the line, wishing he made a change into something he actually wanted. I wish I knew the right words to say to him but it makes me sad because he’s unhappy, yes he can leave, simple as that but he is thinking about his children. What’s good advice to give here?