If you don't know the individuals involved your judgement is based on ignorance.
I know that the man is 29 years old and has children.
I know that the girl (yes, she's a girl, not a woman) is 17 years old and lives with mum and dad.
If you honestly, genuinely think that the two could be in any way comparable with regards to 'maturity' (though I'm yet to hear a satisfactory definition of what that means other than excusing adult men having sexual realtionships with teen girls) then I'll probably never convince you otherwise.
And of course you don't know them either. There's always this assumption that the younger partner (99% of the time a girl) is magically 'mature' but for all we know she could just as well be very immature, and that's why she's fallen for a dad 12 years her senior, and that is why he is attracted to her.
People are not just an age...there will be common interests, humour, physical attraction, personality.
How does this work though? And isn't it funny that the 'not just an age' thing almost only works in favour of men?
As I said above, I teach young people that age or slightly older. Many of them are indeed funny, clever and yes, physically attractive. However, I would never allow myself to even entertain thoughts of how fit they are - if such a thought momentarily comes into my head I remind themselves of their youth and immediately dismiss it - let alone 'date' one of them. Because they are still at a formative stage in their development and should spend it with someone their own age. And this despite what I said above about how, despite all the excuses made here for older men dating teenage girls but rarely the reverse, for an older woman to date a very young man is probably a lot less risky than the other way round.
Most adults would immediately dismiss the idea of dating a teenager, however 'attractive'. This man must have known this girl was 17 very soon after he met her - inevitable unfounded speculation that she was 'mature' and 'looked much older than her age' aside. And he chose to pursue a sexual relationship with her fully aware of that. Relationships don't just 'happen'. The individuals involved make them happen. And this 29 year old dad chose to 'date' a 17 year old girl who lives with mum and dad.