AITA for refusing to pay for my ex-wife’s sister’s college?

A 30-year-old guy from a wealthy family ends his four-year marriage eight months ago when he learns his ex-wife Claire was cheating with an old flame. During the divorce, a bigger bombshell drops: Claire’s younger sister Cindy, 20, knew all about it, stayed silent, and even helped cover it up.

Before the truth came out, he’d generously promised to cover Cindy’s full medical school tuition—and even paid one semester post-divorce, not wanting to punish her for her sister’s actions. But once her complicity surfaced, the betrayal hit hard, and he pulls the funding, telling her to find loans or other options.

‘AITA for refusing to pay for my ex-wife’s sister’s college?’

The marriage crumbles when he discovers Claire’s infidelity with an ex-boyfriend, leading to a quick divorce eight months ago:

He’d already committed to funding Cindy’s med school due to family wealth, and initially sticks to it despite the split:

When the college emails about upcoming fees, he redirects them to Cindy, making it official:

Her father reaches out calmly, asking if he’d reconsider—the guy holds firm, and the dad accepts it (noting the father was supportive during the divorce):

The choice splits opinions among friends and family—most back him, but some, including his mom, urge honoring the promise since it’s easy money for him, while his dad agrees with pulling out:

Betrayal in family ties cuts deep, especially when generosity meets deception. The guy stepped up with an extraordinarily kind offer—fully funding med school for his then-sister-in-law—out of pure goodwill and family wealth. Revoking it after learning she actively helped conceal his wife’s affair isn’t petty revenge; it’s a direct response to shattered trust and boundary violation.

Promises, even generous ones, aren’t unbreakable legal contracts in personal relationships—they often carry implicit conditions like mutual respect and loyalty. Financial experts and therapists frequently point out that continuing support after betrayal can enable toxic dynamics and erode self-respect. Cindy’s choice to stay silent (and assist in hiding) directly contributed to prolonged pain; withdrawing the gift aligns with natural consequences rather than outright punishment.

The “money is no object” argument doesn’t create obligation—wealth doesn’t mean endless giving to those who hurt you. Critics like his mom, urging him to pay anyway, are free to contribute themselves if they feel so strongly. Suggesting he “be the bigger person” ignores that true maturity includes protecting oneself from further exploitation.

Moving forward, holding firm reinforces healthy limits while any lingering guilt is normal but misplaced. Short therapy could help process the double betrayal without second-guessing a reasonable decision. Cindy, entering a high-earning field, has viable paths like loans—many doctors build careers that way without issue.

Here’s what people had to say to OP:

Online users unanimously backed the guy, stressing actions have consequences and no obligation remains after betrayal:

Most called straight NTA—Cindy’s role in hiding the affair killed any goodwill, and critics can pay if they care so much:

This boils down to betrayal’s fallout—generosity offered freely, withdrawn after trust gets shattered by complicity. The crowd sees zero obligation left, with consequences fitting the choice to hide infidelity. Would you keep funding someone who helped torpedo your marriage, or draw the line at betrayal? Ever faced pressure to “be the bigger person” with money on the line? Spill below!