The following site is the Genealogy.com Web site linking to the surname Weiss-
Be prepared to spend LOTS of time!
"Notes to "HOUDINI" by Kenneth Silverman, while hard to get now, has a lot of information. There was also a Society of American Magicians committee that looked into the facts surrounding Houdini's birth. Info on that can most likely be found by asking any SAM official.
It is my understanding that Hardeen (Theo Weiss) had at least one child but you would need to contact Sid Radner in Florida to find out who they were or if any were still alive