There is an interpretation I’ve seen (and I’ll have to edit this answer later to add references) that Job’s children were not actually killed: they were merely hidden away and he was told they’d died. In addition to answering Why did God allow satan to take lives just to prove that Job is loyal?, this takes care of your question as well: he got his original ten children back, plus another ten for a doubling.

Malbim on 42:13 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 Why did God allow satan to take lives just to prove that Job is loyal?, this suggests a that children are not included in “all that Job had” (42:10) to be doubled.

There is an interpretation I’ve seen (and I’ll have to edit this answer later to add references) that Job’s children were not actually killed: they were merely hidden away and he was told they’d died. In addition to answering Why did God allow satan to take lives just to prove that Job is loyal?, this takes care of your question as well: he got his original ten children back, plus another ten for a doubling.

There is an interpretation I’ve seen (and I’ll have to edit this answer later to add references) that Job’s children were not actually killed: they were merely hidden away and he was told they’d died. In addition to answering Why did God allow satan to take lives just to prove that Job is loyal?, this takes care of your question as well: he got his original ten children back, plus another ten for a doubling.