I think mikeyfly assumed that you were adding your parents to your account and not merely as friends and family.
If you add your parents to your household account then the avios for a redemption will be drawn from the avios balances of all the members of the household account. Just adding your parents as friends and family merely allows you to redeem your avios for them -- you cannot pool your avios with them and they cannot access the household pool of avios.
From the Guide:
Note: Avios cannot not be pooled with anyone who is added to your Family and Friends list, you can only share Avios in this way with individuals who live at the same address as you and are part of your Household Account.