AITA for locking my bedroom door at night to keep my dad’s girlfriend’s kid out?

Family life can get really complicated—especially when unexpected guests turn your personal space into their playground. Recently, a 15-year-old found herself caught between conflicting roles: the need to protect her privacy and the unspoken expectation to act like a big brother to her dad’s girlfriend’s 5-year-old son.

For months, the young teen endured a relentless barrage of attention—sleepwalking intrusions, piggyback requests, and even physical play that disrupted her sleep. It all became too much, and in a bid for some much-needed solitude, she decided to lock her bedroom door at night.

This simple act of self-care, however, ignited a firestorm at home. Her dad’s girlfriend was furious, claiming that her son’s feelings were hurt and that her actions were tearing the family apart. Meanwhile, her dad insisted that she shouldn’t lock her door. Caught in the crossfire of blended family expectations and personal boundaries, the teen is left wondering: Am I the asshole for putting my own peace of mind first?

‘AITA for locking my bedroom door at night to keep my dad’s girlfriend’s kid out?’

Experts in family dynamics emphasize that setting clear, healthy boundaries is essential in any blended family, especially when roles and responsibilities aren’t clearly defined. Dr. Laura Markham, a well-known authority on positive parenting, reminds us that teenagers are not expected to be responsible for the care of younger children—particularly when those responsibilities infringe on their privacy and sleep.

In this case, the teen’s decision to lock her door reflects a fundamental need for personal space, not a rejection of familial love. Family therapists explain that when one person consistently absorbs caregiving duties that do not belong to them, resentment and stress quickly follow. “Boundaries are not about shutting people out entirely; they’re about creating a safe space for everyone to recharge,” notes Dr. Markham. This means that your right to privacy is valid—even in a blended household—if it protects your well-being.

Moreover, experts argue that expecting a teenager to act as a caregiver or surrogate older sibling for a younger stepchild sets up unrealistic expectations. It blurs the lines between familial love and parental responsibility

While the 5-year-old might naturally crave attention and seek a sibling figure, it’s the duty of the primary caregivers—in this case, your dad and his girlfriend—to provide that support without imposing on your personal space. Your act of locking the door, when done in a safe and reasonable way, is a clear statement that your well-being matters too.

Additionally, fire safety experts have clarified that using a proper locking mechanism (one that can be quickly disengaged in an emergency) does not necessarily compromise safety. Instead, it provides a controlled environment where the boundaries are respected. In any family setting, clear communication about roles and limits is critical.

If your dad’s girlfriend expects you to be a “big brother” at night, then that expectation should be discussed and managed—rather than imposed without your consent. Open dialogue between all adults in the household is needed so that responsibilities are fairly shared, and personal space is maintained.

In summary, experts agree that your need for privacy and uninterrupted sleep is not only justified but necessary for your overall health. By setting this boundary, you are advocating for a balanced family dynamic where everyone’s needs are respected. Your dad and his girlfriend should work together to reassess caregiving expectations rather than forcing you to compromise on your own well-being.

Here’s the feedback from the Reddit community:

The Reddit community has voiced strong support for your decision. As one commenter noted, you’re not obligated to act as a caregiver for someone else’s child—even if they are part of the new family mix. Other responses highlight that your privacy is paramount and that expecting a teenager to shoulder nighttime parenting duties is simply unfair.

Many agreed that rather than locking your door, a proper conversation with your dad about balancing responsibilities could have been the first step. However, most responses converge on the view that protecting your own sleep and space is completely reasonable, with several suggesting alternative safety measures if needed.

In conclusion, the boundaries you’re setting aren’t about rejecting family—they’re about preserving your own health and well-being. Blended families often come with mixed expectations, and it’s crucial for all adults involved to clarify roles and responsibilities. Have you ever had to set boundaries that went against what others expected?

What strategies helped you communicate your needs effectively in a challenging family dynamic? Share your thoughts and experiences below; your insights may help others navigating similar situations.