One's life and ambitions don't end when one becomes a parent.

For those whose greatest ambition (confirmed by their actions) is to be a responsible parent, great!

The reality for actual parents is that parenting is a constant struggle between one's ambitions and one's responsibilites.

Yes, this is an extreme case, but how is this much more selfish than parents who get divorced?

One might argue that if a father cannot always and in all conditions put the children first, he should not be a father.

I'd argue that this is overly simplistic. Honestly and strictly applied, it would mean that we'd almost never reproduce.