Hi ksd23,
In 2011 the government introduced a scheme called Specified Adult Childcare Credits (SACC) whereby grandparents can claim a Class 3 National Insurance credit for each week, or part-week, in which they cared for an eligible child.
The parents Child Benefit itself will not be affected, but the SACC works by transferring the Child Benefit National Insurance credits from the parent to the family member.
This is only done, however, as long as the parent does not need the credits themselves.
You can find out more about this here:
Apply for Specified Adult Childcare credits
Including how to apply.