What's wrong with this picture?

Last weekend, my dad and I visited our old house in the southern Netherlands. It was a Sunday evening, and through the windows I could see people doing whatever is they do on Sunday evenings. Sitting on the couch, that sort of thing.

They were people who weren't us, people who didn't know us, people who probably didn't care that we used to eat there, sleep there, laugh there, cry there, live there. Maybe I had expected to see us—younger versions of us—in there. If I felt anything, I felt that it wasn't ours anymore.

Once, there were tulips. Once, the neighbors' children and I built a giant castle out of snow.

Back at my parents' house, I searched through every album and finally found this photo. It's probably something like twenty years old.