On what basis do we draw this conclusion? The inspired record indicates that Noah’s sons were already grown and married when God commanded Noah to build the ark.
يُشِيرُ ٱلسِّجِلُّ ٱلْمُوحَى بِهِ أَنَّ أَبْنَاءَ نُوحٍ كَانُوا رَاشِدِينَ وَمُتَزَوِّجِينَ حِينَ أَوْصَاهُ ٱللهُ بِبِنَاءِ ٱلْفُلْكِ .‏