Some people then gave OP tips on how to respond next time her sister or family expects her to take care of the kids:

“If you cannot escape a day with the kids, weaponize your incompetence. Be a bad babysitter without harming the kids. Text your sister and mom incessantly while they are out. Your brother-in-law. Dad. Everyone. Bombard them with questions. All. Day. Constant barrage. ‘Is this too many carrots? Can he have this much of a sandwich?’ … She cannot dump kids and enjoy her day off. Be the problem, OP, not the solution.”

—u/DefinitelyNotAliens·

“Next time dear old sis shows up on your doorstep, have a bag packed and ready to go and see if you can go to a friend’s or family member’s house while she’s there. If that isn’t possible, lock yourself in your room and only come out to use the restroom and eat, then immediately lock yourself back in…they’ll get the hint…”

—u/Obsidiannight2010

Source: https://www.buzzfeed.com/alanavalko/lost-passport-avoid-babysitting-family-vacation