It is somewhat amusing that BOTNS is a time travel story, and Severian sleeps with his grandmother, but the means of so doing is not time travel (at least not by severian).
Any SF stories where the grandfather paradox is a result of the grandmother being brought forward in time (and then sent back?)
"I am an impure thinker. I am hurt, swayed, shaken, | paul + | + elated, disillusioned, shocked, comforted, and I | --|-- have to transmit my mental experiences lest I die." | + | +
-- Eugen Rosenstock-Huessy | pduggan at world.std.com