The question remains as to who Blueblood's distant grandparent was. Since Faust said that Blueblood was also Luna's nephew, the arrogant noble isn't the result of Luna and Crashing's union. 

It's possible that Blueblood was a descendant of Torrential since over 52 generations and the intermingling of the three pony tribes it isn't a surprise that a unicorn was born into the bloodline. It's such a same that Blueblood is already dead, since their mutual hatred of the horned pig would have been a wonderful bonding experience for Torrential and his grand daughter in law Rarity.

Anyone else want to try and lay claim to Blueblood?