“Corvus! Oh, I’ve missed you, friend! A day has not gone by that I have not thought of you, brother! Oh, your cold, dead skin smells of ammonia, bruva-friend!”

No one would believed you. If you told someone with no knowledge of 40K. That these two are actually brothers.

But then again the Primarchs as a family are more like if te Emperor pulled a Peter Griffin on donating to the sperm donors.