1. "Your sister is better than you at [fill in the blank]."
Maybe you’re trying to motivate one grandchild to try harder, but pointing out her sibling’s Serena Williams-style tennis serve isn’t going to push her to ace her own next serve, says Jodi R. R. Smith, author of The Etiquette Book: The Complete Guide to Modern Manners. Children want their grandparents to be judgment-free cheerleaders.
Better to say: If your grandchild asks if you think her sibling is better at something, you can say, “Yes, she’s good, so let her play tennis while you wow us on with your swimming,” or whatever her forte is. If she doesn’t ask, keep mum unless you’re saying how proud you are of, well, whatever she does.