Play favourites: Most grandparents don't realise that they're doing it, but using preferential language toward their grandchildren can cause emotional wounds that never heal.
Make moms feel guilty about their feeding style: A mom's choice to breastfeed or bottle-feed is her own, and not every mother is able to choose breastfeeding. Condescending opinions from grandma about how to feed the baby are completely unnecessary.
Air Mom and Dad's dirty laundry: While the stories of your kid's teenage mishaps may be funny to relay to adults, they'll only encourage small children to disobey. Save it for when they're older.
Send everybody on a guilt trip: "I'll only be alive for a few more years, but if you want to spend Christmas in Hawaii, that's fine . . . " is exactly the type of behaviour that should never occur.
Ignore set diet rules: If a child's parents have them on a dairy-free, sugar-free, or gluten-free diet, it's not the grandparents' place to change it. Breaking diet rules can be very risky!
Bad-mouth family members: No matter how frustrated a grandparent is at their kids, they should never express it in front of their grandchildren — talk about traumatizing!