This is Sean Whalen (prion).
When I was thinking about Borski's idea that Aunt Jeannine from The Fifth Head of Cerberus is an abo (which I believe), I remembered another point that backs this up. The use of a spiral staircase as a metaphor for genetic relationship (a spiral is a helix, as in DNA) has been discussed concerning No. 5 and Phaedria, but it also relates to Aunt Jeannine. When she is taking No. 5 down to her room after she catches him, she walks with him until they reach the corkscrew (helical) staircase when she floats down the center instead. No. 5 continues on the staircase, without her. So this indicates that there is no relationship between the two.
These helices-as-DNA also include the spiral in the library that No. 5, David, and Mr. Million use, but I don't see any additional significance besides showing that they are related as well.
Another point is that when Jeannine first catches No. 5, he has the feeling that she can see him equally well when there is no light as when the fireworks are exploding, indicating that she has night vision.
prion