Are OSAP grants considered taxable income?

My two son's received OSAP grants - one significantly more than the other.  The higher recipient has received 2 T4As (provincial and federal) for what I assume is the grant portion of the OSAP advance and through the CRA auto-fill is populating the other income field (~$6500) therefore increasing his income and resulting in a tax owing position.  My other son had a T4A but the auto-fill did not populate the other income field (~$400) and therefore is not reflected in his total earnings.  I'm confused why they seem to be populating differently AND I thought that while a full-time student there was no repayment on loans and grants did not count as taxable.