Hi,
They don`t always follow the convention but yes the first son could be named after his paternal grandfather. The following is a guide only:
First Son - Father`s father
Second Son - Mother`s Father
Third Son - Father
Fourth Son - Father`s eldest Brother
First Daughter - Mother`s Mother
Second Daughter - Father`s Mother
Third Daughter - Mother
Fourth Daughter - Mother`s Eldest Sister
Regards,
Mo