Dr. Halsey's personal journal

Dr. Halsey's personal journal is a booklet co-written by Eric Nylund and is included with the Halo: Reach Limited and Legendary editions. Not much is known about it, other than it covers various things in the Halo Universe and is written through the eyes of Catherine Halsey herself.

Description
It is in this journal that several important revelations are made regarding Cortana, Her relationship with Captain Jacob Keyes and Miranda Keyes. per the journal, she states in an indirect fashion, that she and Captain Keyes had a relationship and that though Halsey had been close with Miranda, they had drifted apart.

Furthermore, it is stated that when Miranda received command of her first ship, In Amber Clad, she invited Halsey to attend the ceremony but Halsey refused stating that "I didn't go. Because her father would be there? Because I am neck deep in the final stages of a half-dozen projects? I know why I didn't go. I don't want to say it". From this it is inferred that Halsey is the mother of Miranda Keyes.