Looks like whoever wrote that particular sentence on Old Chief Smoke's wikipedia page slipped up. Elsewhere on Smoke's page you'll notice that he's said to be the brother of Walks As She Thinks (Red Cloud's mother), and his children are mentioned as Red Cloud's cousins. If you follow up on the source they used, it also makes it clear that Red Cloud is not Smoke's son. That Lone Man was Red Cloud's father is attested by Red Cloud's nephew, He Dog.