(urth) Sister?

[Lee Berman]

>Jeff Wilson- Severian's lack of mention of a sister suggests to me that either he 
>came without one, or that any on record are no longer locatable.
 
This is a plausible explanation and it surely could be what Gene Wolfe had in mind
with regard to "severa".
 
Among the most popular alternate explanations I've seen are that Severian's sister is the 
witch, Merryn as hinted at in Return to the Whorl. Another is that he discovered that his 
sister is someone he had sex with and doesn't want to openly reveal it, managing to drop 
(conscious or not) hints about it, similar to the hints regarding Dorcas being his 
grandmother and similar to the hint Agilus drops that he and his sister have a sexual 
relationship. 
 
I think Wolfe leaves it to each reader's personal preference which explanation to lean
toward. There is even latitude for those who are comfortable with the ambiguity of three
(or more) parallel explanations and no need for choosing one over the others.