This article or section includes speculation, observations or opinions possibly supported by lore or by Blizzard officials. It should not be taken as representing official lore.
His surname fuels speculation that there may be a relative of the Windrunner family that has not been brought into the storyline yet. This could imply that the Windrunner family — already parted between the Forsaken, the Alliance, and some unknown fate in Outland — could have member in the blood elf community. This blood mage could also have pushed for the entrance of Silvermoon and the blood elves into the Horde. The similarity of the names implies that Sylvos and Sylvanas are closely related, perhaps twins — a rare occurrence among high elves,WoE 9 however this is unlikely the case as neither Vereesa or Alleria have made any mention of him when referring to their sibling, Alleria has only recently made mention of Lirath (Beyond the Dark Portal). Whatever the case, it is stated that besides her two famous sisters she also has or had other family members — a grandfather (alive), an uncle (dead), three brothers (dead), her parents (presumed dead), and various other relatives WoE 11. Furthermore since Lirath was referred to as the "youngest brother", it may be assumed that he was not the only male sibling, however it is unknown whether Sylvos is sibling, cousin, or other relation. However, with the release of Night of the Dragon, this mysterious blood elf could possibly be Zendarin Windrunner.