I think Ranmaru and Raiga are kind of based off of Mori Ranmaru and Oda Nobunaga, because Ranmaru's lord (Oda Nobunaga) found him he was only six years old (which is about the age I think Ranmaru is) and from that point on kept him as his valet (which in that period of Japanese history was pretty much your elite bodygaurd-- it was a 24/7 job and the valet was the last line of defense for his/her lord.) Ranmaru was also known to have been very handsome in a slightly feminine way.
Another interesting thing is that Oda Nabunaga was often rumored to be immortal, because whenever he was cought in a trap that would have killed a normal lord he managed to get out. This could be where they got the inspiration to have Raiga almost get killed and then survive...
However, if I am right about them being based off these two historical figures, then it should be noted that Mori Ranmaru and Oda Nabunaga died together in an ambush.