The hiei dating game
He currently is the 3rd Raikage and is married to Yotsuki-Iga Sachiko and has one biological son, Yotsuki Shun, as well as an adpotive son, Yotsuki Akira.
Kenshin has not divulged any theories as to why to his son.
I personally am deleting my copy of Of Cybertron and will repost everything once we're done editing.
These chapters will take place WAY later on the timeline, after Strike is grown.
Hiei is the eldest son of Yotsuki Kenshin, a shinobi who served with the first Raikage during the war and helped unite the clans after the war.