Ondrell Harding, 21, was arrested Monday night south of Seattle as a suspect in the beating death of a 50-year-old man in Seattle on Saturday, Seattle police Detective Mark Jamieson said.
He has been booked into King County Jail and is being held without bail.
Ondrell Harding is the older brother of 19-year-old Kenneth Harding, who died after being shot while running from police who were conducting a San Francisco Municipal Railway fare check in the Bayview District on July 16.
Police said Kenneth Harding fired at officers and they returned fire. An autopsy later determined that the bullet that killed him did not come from a police gun, and police said he might have shot himself.
The incident has sparked protests in San Francisco, and Harding's family held a news conference on Monday to announce that they were considering legal action against the San Francisco police.
At the news conference, Kenneth Harding's mother said her son had come to San Francisco to launch his career as a rap artist. She said his brother has a recording contract with a record label in San Francisco and planned to help Harding.
Seattle police could not confirm how Ondrell Harding was taken into custody, but an attorney working with the family on the possible civil case said Tuesday that Harding was planning to turn himself in.
Prior to his arrest, Seattle police alerted San Francisco police that Harding was being sought for questioning, in case he was in the Bay Area, San Francisco police spokesman Albie Esparza said.
Kenneth Harding was a person of interest in a separate Seattle case -- the July 13 murder of a 19-year-old woman -- at the time of his death, police said.