Line 30300 is for the spouse/common law amount, having a child doesn't affect this credit.
On the Schedule 5 calculations for Line 30300, line 2 will only have an amount if you are claiming the Canada Caregiver Amount for your spouse/partner. Line 5 is the amount of credit you are getting. If it is zero, either your spouse/partner's income is too high (see the amount in line 4), or you answered No when asked if you want to claim the credit (line 4 will be 0).
