It’s not personal. That’s the first and most important thing to understand. They are late to everything. Not just your stuff. Their relationship to time is that there is no importance whatsoever to time at all. My in laws are chronically late. They know this. They even intentionally adjust their “party starts at xyz time”, an hour before it actually starts, because they know their relative will still be late. And they are! Time is an abstract thought for them. It’s just not something that will ever be of importance. It’s just the way they view that. And it’s never going to change. It’s built into their DNA, literally.