[Malbim on 42:13](https://www.sefaria.org/Job.42.13?lang=bi&with=Malbim&lang2=en) quotes an interpretation by Nachmanides
that Job’s children were not actually killed:
they were merely hidden away, and he was told they’d died.
In addition to answering _<https://hermeneutics.stackexchange.com/q/9043/410>_,
this suggests a that children are not included in
“all that Job had” (42:10) to be doubled.