Blackfur is one of two notorious outlaws from Adventure Bay's past, along with Wild Wilbur. Both where outlaws in different eras of Adventure Bay's history, as Captain Blackfur was a pirate during the Age of Piracy, while Wilbur was an outlaw during the Wild West. Both also left behind their hidden treasure, which would later be found by Ryder & the PAW Patrol.
Though unconfirmed, it is possible that Captain Blackfur may be Rubble's ancestor or a blood relative. Both are English Bulldogs that are known to live in and/or around in Adventure Bay. However it is also possible that they are simply the same breed and are not blood related.
Though he is viewed as a romanticized figure as most famous historical pirates usually are, as a pirate, he was for all intense and purposes a criminal as piracy is a criminal act. However it should be noted that during the real world Age of Piracy, it was not uncommon for pirates to work legally as privateers (pirates licensed by a nation to legally plunder ships of enemy/rival nations), so it is possible that Captain Blackfur could have obtained his pirate treasure legally. Of course, it could have been obtained both legally (through privateering) and illegally (via piracy) as it was not uncommon for privateers to become pirates and vice versa.
Captain Blackfur's namesake: Edward Thatch or Edward Teach, also known as Blackbeard.
Despite being a pirate and criminal, it is shown by his final pronouncement that he was noble and thought well enough of the people and town of Adventure Bay as he bequeathed his treasure be returned to the townsfolk by whoever found his hidden treasure.