So he's probably Shanks' father now. Interesting.
Now, the real question becomes: Why did the Gorosei/CDs not disown Shanks like Doflamingo then? He was Roger's protege who wore his hat. He gave said hat to Luffy.
This really is leading me down that grey territory with Shanks. They respect him enough even as a pirate, and he clearly hides his business as a CD with them (i.e. his cloak), so what gives?