Gravis was first a bit surprised, but after thinking about it for some seconds, he realized that it actually made sense. How big was his family? On top of that, how long did his siblings live? For the first five to fifteen births, a sibling might be interested, but after that?
At some point, it was just more of the same. At the same time, there wasn't much that connected them to their parents. Yes, the first couple of hundred years, they might still feel a connection to their parents, but after that?
One had to remember that most of his siblings had been raised to the Immortal Emperor Realm by his father. They would have their own families already, and the restriction of visiting their father only a couple of times could also estrange them.