I met and somewhat got to know Rick Stanley, Elvis' stepbrother. I believe Elvis' dad married Rick's mom at some point in the '60s. Anyway, Rick had a couple of brothers and when they were late teenagers, they were added to the security detail. When I met him, Rick was in seminary, having became a Baptist minister and went on to Pastor one or two churches in Florida and speak at other churches around the country. Like his step-brother, unfortunately, Rick's life started to spiral downhill in the 2000s for some reason. I was only in touch with him in the mid-'80s so I don't really know what happened. I've just read a little here and there and those I know that also knew Rick haven't been in touch in decades.
One thing that Rick told me about Elvis was how kind he was. Immediately upon meeting his "new" brothers, Elvis welcomed them and pretty much bought them anything they wanted.
As far as Elvis' impact, he is probably the biggest popular culture figure in history. 50 years after his death, he still has many fans. There are a lot of guys, including a HS friend of mine, who make good livings as Elvis tribute artists and probably will for many years. Name one other icon that can say that. Frankly, no one knows who the Beatles are anymore and even if they do, they can't name them individually. Their tenure together was nowhere near the amount of time Elvis' career was and while you could put together a Beatles cover band, people would want more -- the Stones, other '60s stuff, and even '70s and '80s stuff.