Tell Me About It: Sister is sleeping with her twin's new in-law

Adapted from a recent online discussion.

Question: I married the man of my dreams, only to return from our honeymoon to find that my twin sister has been secretly sleeping with my now brother-in-law. Problems have since arisen.

(1) I'm upset my sister is sleeping with someone I now consider family, and for whom this is essentially just a booty call. (He won't even let her tell people they are friends, and tells everyone he doesn't even like her.) She keeps telling me he'll realize he actually loves her "one day."

(2) She now thinks it's appropriate to spend three to four nights a week at my in-laws' home and invite herself on outings she wasn't invited to. My mother-in-law and I have always been on shaky footing, and now I'm fighting jealousy over someone who isn't even dating into the family. Help! I don't want to be mad at my sister, but she's making me crazy.

Answer: No she's not. You're making you crazy. Your sister's choices sound embarrassing for you, but they're still hers to make. Trying to manage the behavior of these two adults will only risk further strain with your in-laws. Focus on your spouse, focus on your relationship with your mother-in-law, and (only!) when your sister brings it up, express concern that she's setting herself up to get hurt. That's it. For all else, deep breathing.

Question: What's so wrong with being a pleaser? I know it can go too far - but wouldn't the world be a better place if we all just took a deep breath and sucked it up, worked on pleasing people for their quirky wishes, and saved our ground-standing fights for stuff that really matters?

Answer: The devil is in the "it-can-go-too-far" details. If you know yourself well, are comfortable with your strengths, are mindful of your weaknesses, and don't give a @!$ whether people like you, there's little to lose in indulging people's quirks.

If instead you are choosing to indulge people because you're afraid to upset them or want to win them over, then here's what happens: You're going to gauge your behavior on getting a specific response from others - and you will pay more attention to giving them what they want than to how much of yourself you're compromising to achieve that end. That's when you find yourself scrambling to serve everyone else and becoming no one you recognize, or even like.

Funny thing is, people are more likely to "please people for their quirky wishes" when they're, say, dealing with in-laws, on the theory that it's important to please one's spouse or immediate family - but it actually makes more sense to indulge when there's nothing on the line. A stranger on public transportation, a colleague you don't work with closely, etc. - there's no precedent to worry about there.

With family, what matters most is finding a way to get along over the long haul, and that purpose is better served by presenting as little artifice as you can, and contorting yourself as little as possible, without being rude. People coexist better - or at least more sustainably - as a particularly civil version of themselves.

Chat with Carolyn Hax online at noon Fridays at www.washingtonpost.com.