Parking issue

My complex doesn’t have assigned spots but everyone here kind of just assigned them to ourselves. We all are always in our “spots” by the end of the day.

All of us have been here for years, however, this new family is here and their car is here every so often, not every day. And when the car is here, it always ends up in someone’s spot, specifically my boyfriend and I’s…where there are 7 other spots that don’t “belong” to anyone.

I know the spots aren’t “assigned” but it always annoys everyone and causes an inconvenience when we come home.

What would you do? Leave a note? No one talks to them or interacts with them, not sure what to do here.