I have worked 10-12 hours a day throughout all of my working career (from 19yo onwards). This is in central Europe, and I'm not even the hardest worker around.
I also have hobbies and a social life - but it has consequences.
Family and children are entirely 100% impossible in this lifestyle without a stay-at-home partner. And unlike previous generations, stay-at-home partners are no longer a thing.
(Edit: to make it clear, I am not making a judgement, nor wishing for a stay-at-home partner - I'm entirely in favour of everyone making their own choices in life.
I am just pointing out that younger generations are now living in a totally different environment from previous generations, where a stay-at-home wife was the default. Which is yet another component in the birth rate equation.)
Props to you man, I have no kids and still barely manage to have hobbies and social life with just normal full-time hours. I do need a lot of time to sleep and simply rest and do nothing, so that is a factor.