AITA for not letting my sister-in-law (SIL) have her dream nature-themed ‘cottagecore’ home because I secretly purchased the land to prevent it from being built on top of a protected ancient burial site?

I (31F, Sarah) have complicated feelings about my SIL, “Ava” (26F). She is obsessive about aesthetics, particularly “cottagecore,” and sustainability, but it always seems to revolve around creating curated digital moments rather than genuine environmental respect. My hard-working brother, “Liam” (29M), recently confided in me that Ava found their “perfect patch of untouched wilderness”—a remote, idyllic woodland with majestic old oaks and unique rolling topography. She spent months planning her ultimate off-grid tiny home there.

Here is the secret: that land is technically unregistered, but for generations, local historians knew it was a documented indigenous burial mound from the early 19th century. Ava and Liam didn’t know the history. When the private owner quietly listed it, Ava immediately made a significant offer using their entire savings.

The moment I learned about her plan, I was horrified. I refused to let her build her whimsical, aesthetically curated, sustainable home literally on top of people’s ancestors. Knowing how fixated she gets, I didn’t think explaining it would stop her; she’d likely argue “it’s deep underground, dead people don’t care about aesthetic choices,” and her life in a tiny home matters more.

Instead, I used my own life savings to secretly outbid them at the last second. The day after the sale closed, I got the land legally designated as a protected, non-buildable conservation easement in perpetuity.

The feature image below captures the moment of reveal. Yesterday, when Liam mentioned Ava was heartbroken because they lost the land to a generic “developer,” I confessed my role. I told her why I did it.

Ava is now absolutely hysterical. She calls me a controller who “used her dream as a stepping stone to be a self-righteous hero.” She claims I “manipulated” the situation rather than respecting her intelligence. Liam is trying to be neutral but thinks I was “unnecessarily sneaky” and that my methods were cruel. My parents think I could have just trusted them with the knowledge.

Now I’m being frozen out of all family events. My intention was to protect a sacred site, but I’ve crushed my brother’s future home and Ava’s dream.

AITA?