How did they know Regulus died?

In OotP, Sirius talks about his younger brother joined the Death Eaters, tried to back out and was executed. However, DH reveals that Regulus had found out about the locket Horcrux and tried to destroy it only to be overwhelmed by the Inferi and killed.

Did Regulus fake his death?

Perhaps, knowing that he was facing certain death at the hands of Voldemort, he decided to fake his own. Then, with the Death Eaters (many of whom were his family members) sure of his demise, he would be able to go after what he believed to be Voldemort’s only Horcrux.

Is Regulus Black related to Voldemort?

—Regulus’ parting letter to Voldemort [src] Regulus Arcturus Black ( 1961 – 1979) was an English pure-blood wizard, born to Orion and Walburga Black, and the younger brother of Sirius Black. He was a member of the House of Black, an old wizarding family, which probably started around the Middle Ages.

Why did Regulus Malfoy defection to Voldemort?

Regulus worked out that the locket was a Horcrux and was the reason behind Voldemort’s immortality. This was the deciding factor in Regulus’ defection.

How did Regulus Potter become a Death Eater?

He attended Hogwarts School of Witchcraft and Wizardry in 1972 and was sorted into the Slytherin house. Regulus became a Death Eater in his youth, but defected when he found what Lord Voldemort would do in order to reach his aims. Regulus also learned about one of Voldemort’s Horcruxes and decided to destroy it.

How did Harry Potter and Ron Weasley find out about Regulus?

In 1997, Kreacher told Harry Potter, Ron Weasley, and Hermione Granger of Regulus’ attempt to destroy the Horcrux, having been there himself, as the trio also sought to destroy Voldemort’s Horcruxes. They then realised that Regulus was R.A.B. that was signed on the note to Lord Voldemort.