Yep - again, she showed up in the books, but not in the show. Her name is Judith (what is with J names in that family?) and she is a cellist in the Portland Philharmonic or something like that. Plus he also has two brothers (or I suppose half-brothers strictly speaking), who were mentioned in the books but never really "seen" as such.
However, it was in the last season of TNG that people complained that there were too many episodes involving family members coming aboard the Enterprise
. So maybe it's for the best that not as much attention was paid to the crew's family members on DS9. On the other hand, the stationary nature of DS9 as opposed to the constantly moving Enterprise
would make family members more likely to show up randomly.