Perhaps parents talk to their kids about it. There's no reason for anyone else "to determine" their situation, is there?no one can give answer of this question because different people may convert into different beliefs for various reason and there is no way to determine that who converted for spiritual reason and who converted for any material incentive especially when we talk about past conversions
if you say so, BTW not a single IVC site has been found in Ganga or Dravid region.

