AITA for telling my kids why I don’t buy their half sibling anything?

Family finances and blended relationships can be incredibly sensitive topics, especially when infidelity is involved. In this case, a father of two (10‑year‑old son and 9‑year‑old daughter) recounts how he explained to his children why he refuses to buy gifts or cover expenses for their half-sibling—the result of his ex-wife’s affair during their marriage.

Despite having always been transparent about the half-sibling not being his biological child, the conversation took an unexpected turn when the ex-wife, struggling financially, pressured him to help out. When he firmly reiterated his stance to his kids, she lashed out, accusing him of cruelty. Now, he wonders if his honest explanation makes him the asshole or if he was right to set such clear boundaries.

‘AITA for telling my kids why I don’t buy their half sibling anything?’

Family and relationship experts emphasize that setting clear financial and emotional boundaries is crucial in blended family situations—especially when the origins of the relationship involve infidelity. Experts like Dr. Laura Markham note, “Honesty about your values and boundaries is essential in guiding children to understand their family structure,” which applies here as the father sought to protect his own children’s best interests.

When a parent’s past decisions have directly affected the family dynamic, it’s both reasonable and necessary to delineate responsibilities clearly. In this case, the father is asserting that his obligation is only to his biological children, not to cover the financial needs of a child conceived through an affair.

While the ex-wife’s argument for unity and shared responsibility may come from a place of wanting a stable family environment for all the children, experts agree that boundaries should be maintained to avoid blurring roles and responsibilities. This approach helps ensure that the children receive consistent expectations and protects the parent’s financial autonomy—an important consideration when past behavior has already disrupted the family’s equilibrium.

Here’s the input from the Reddit crowd:

Community reactions on platforms like Reddit are mixed but often sympathetic toward parents who must make tough choices in complex situations. Many commenters agree that if you’re clear about your responsibilities and have been upfront about the family’s structure from the beginning, you’re within your rights to maintain that boundary.

Others, however, suggest that a more gentle explanation might have mitigated the hurt feelings involved. Still, the prevailing view is that a parent’s primary duty is to protect and provide for their own children, and that financial responsibility should not be extended simply because of shared living arrangements or familial obligations, especially when the situation originates from past infidelity.

Ultimately, this story isn’t about being unloving—it’s about setting and maintaining clear boundaries in a complicated family dynamic. The father’s decision to only support his own children financially is rooted in the reality of their family history and his commitment to his biological kids. While the bluntness of his explanation may have hurt his ex-wife’s feelings, it also reinforced an important lesson for his children about honesty and responsibility.

What do you think? Is it reasonable for a parent to limit their financial support to their own biological children in a blended family? Or should there be more flexibility to accommodate all members of the household? Share your thoughts and experiences in the comments below.