WaPo article at link above also has more information about Paddock's life growing up as a child
His brother Eric was a partner in his real estate business
Apparently, Paddock wasn't close to his two other brothers.
Relatives say the roots of Paddock’s loner lifestyle may have been planted July 28, 1960. On that day, when Paddock was 7, a neighbor from across the street took him swimming. The neighbor at the time told a local newspaper that she knew authorities were coming for his father, a bank robber, and she wanted to spare the boy the trauma of seeing his father hauled away by authorities.
His brother Eric was a partner in his real estate business
Even with Eric, he never talked much. They created a lucrative real estate investment business together, but Stephen would only text Eric now and then.
“We didn’t talk much. We talked when there was something to talk about,” said Eric Paddock. “Steve had no help. Steve did not take help. He was a stand-alone guy.”
Apparently, Paddock wasn't close to his two other brothers.