Mom and stepdad buy 11-year-old daughter a birthday trip to 4 amusement parks, ex-husband drags their name through the mud since they didn't include his daughter, the step-sister: ‘If [they] chipped in… we’d gladly take her!'

Elna McHilderson • Managing Editor

Jul 23, 2026 6:00 AM EDT

Should a co-parent be responsible for a child that isn't theirs but is the half-sibling of their kid? Where is the line drawn when it comes to co-parenting?

Many families know divorce too well. It can be an extremely chaotic time for everyone involved. However, many parents work very hard to shield their kids from the chaos and make a peaceful co-parenting situation happen. Is that even possible? Of course! Many families have figured out how to be civil, friendly, and even loving in co-parenting situations. Even when the separated partners have found new partners.

A mother on Reddit who goes by u/DeerExact5881 is trying her hardest to be a good co-parent. Both she and her ex-husband have remarried. They have split custody of their 11-year-old daughter and are keeping the downsides of their split away from their daughter as best as they can. However, her ex-husband had a new daughter with his new wife, and now they expect her to treat her as if she were her daughter too…

Does it mean that she just had a new kid of her own because her ex-husband's daughter is her daughter's half-sister? She never signed up to be a parent to another and she most definitely does not have the finances for another child. She wants them to be loving sisters who get along, but she feels pushed around by her ex and his new wife when it comes to parenting duties to this child that isn't hers.

She and her new husband splurged for her daughter's 11th birthday, but now her ex and his new wife are upset they didn't include her half-sister. She told them that if they wanted to contribute financially to the gift, then she is happy to have her join them. Her ex did not like that and is now bashing her and her husband's name online.

Co-parenting is not as easy as it sounds.

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A happy blonde mom and her small daughter with braids enjoy an ice cream cone while at the amusement park.
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"AITAH For Not Taking My Daughters Step Sister to a Theme Park?"

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A woman poses smiling in front of a Ferris wheel at an amusement park nearing dusk.
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An empty merry-go-round just opens as it awaits customers under a beautiful cloudy sky.
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A mom and her two daughters happily laugh and enjoy a spinning ride at an amusement park on a sunny day.
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$names being rubbed in the mud. I can't be the a\*hole here, I'm so close to just cancelling$

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