Dear Prudence, 
My ex died three months ago. We have twin 5-year-olds. He cheated on me when they were 2. “Mary” was a mutual friend. She got pregnant and they got together after I kicked him out. It was devastating but I tried to be civil and take the high road for the sake of my twins. I moved in with my parents after the funeral. They live about six hours from the city where we used to live. Mary still lives there with her toddler. I telecommute and have a very flexible schedule.
Recently, Mary reached out to me and asked if I would be so “kind” as to take care of her toddler for at least one weekend a month. Her work requires her to work overnight at least three nights a month. With the death, Mary can’t manage it anymore and has no one reliable. Her own family isn’t great. Everyone else is nowhere close to being local. I told Mary no. I wasn’t driving 12 hours round trip to babysit. Mary offered to meet me halfway and tried to frame it as sibling bonding. I told Mary the kids could “bond” during the times they had with their paternal grandparents. Mary called me cruel. I told her to leave me alone. After everything that she put me through, she has the utter gall to ask anything of me. She cried. I hung up.
I feel angry. I feel guilty. I also feel like I have done nothing wrong. I feel I might have messed up my twins’ future relationships with their sibling. My parents and sisters have told me Mary was wildly out of line and delusional to even ask this of me. I still have nightmares about her crying. We were once very close.
—End of Rope