Static Streak

I think prince blueblood is a metaphoric prince.. I think celestia was lonely while waiting for her sister so she befriended some (probably wise) mare and they became so close that she considered her as another “sister”.. well then the wise mare fell in love and had a colt (blueblood) who grew up spoiled and such considering he lived in such luxury.. then around the time luna returned she died from old age or something and wasn’t spoken about on screen.. (just a theory)