Is it even possible that he just doesn't understand how inappropriate his behaviour is?
I've been thinking about it and he's nearly 50. I wonder if this is how mid-life crisis manifest. Men who are otherwise decent reasonable people develop friendships with women and maybe they don't even know it's happening - and wham - they're "in-love" and they think it's just evolved or meant-to-be and all of a sudden they're leaving their wives and destroying a whole family.
They are so unaware/unconcious of their behaviour and how it contributes to inappropriate relationship.
