'Arrow': Slade's Son Reveals [SPOILER]

Discovering that his son is the leader of a group of mercenaries may have been a surprise for Slade Wilson on Arrow tonight, but that wasn't the only unexpected reveal.

Spoilers for tonights episode of Arrow, "Promises Kept," below.

Slade's (Manu Bennett) son Joe turned out to have followed a little too closely in his father's footsteps. When Oliver is captured by Joe's crew, Joe wants Slade to take a literal eye for an eye but Slade doesn't. He frees Oliver and the pair escapes. However, Slade doesn't really want to leave his son. He wants to stop him and thinks the only way he can is to kill him, but Oliver tries to convince him that he just needs to talk to Joe and get through to him.

The two head back and while Oliver deals with Joe's henchmen, Slade and Joe start fighting with Slade trying to explain himself and reach his son. Joe wants no part of it and reveals to his father that he saw Slade kill a Chinese spy when he was a child, but that's not the only secret. Joe reveals that he has a brother that his mother kept secret, a brother named Grant.

This isn't the first time that Grant has been named in the Arrowverse. In the first season of Legends of Tomorrow, "Star City 2046" Grant Wilson is the future Deathstroke going up against the Connor Hawke Green Arrow. In that episode it was revealed that Grant and his army had killed most of Team Arrow, including Hawke's father John Diggle.

With Diggle suiting up as Green Arrow this season and now the confirmation that Grant Wilson exists outside of a potential future, one has to wonder if the Arrowverse is on track for "Star City 2046" to become reality.

Arrow airs Thursdays at 9/8c on The CW.