I was about to say that, how come no one mentions Birthright here?
The usual D&D scenario might not focus too much on this but as you level you you can have something like that. Almost all high level campaigns I DMed would eventually see the characters form a retinue, groups, organizations (like the harpers). A lot of the novels also have this context for the powerful characters, so there's plenty of content out there where for you to be inspired.
[1] https://en.wikipedia.org/wiki/Birthright_(campaign_setting)