If you have adopted a child and you sleep in the same house as your child, you will receive the Mother's Love or Father's Love bonus, which makes healing spells and potions more effective.
http://www.uesp.net/wiki/Skyrim:Sleeping
Does the ability (passive) apply only to healing potions? I'd like to know before I grind skills. I didn't plan on having a family until I noticed the abilities that they can give me.