Prophethood does not guarantee the righteousness of all progeny

قِيلَ يَـٰنُوحُ ٱهْبِطْ بِسَلَـٰمٍ مِّنَّا وَبَرَكَـٰتٍ عَلَيْكَ وَعَلَىٰٓ أُمَمٍ مِّمَّن مَّعَكَ ۚ وَأُمَمٌ سَنُمَتِّعُهُمْ ثُمَّ يَمَسُّهُم مِّنَّا عَذَابٌ أَلِيمٌ

It was said, "O Noah, disembark in security from Us and blessings upon you and upon nations [descending] from those with you. But other nations [of them] We will grant enjoyment; then there will touch them from Us a painful punishment."