My father was from Poland so I know the problems this can bring up.
If the event was pre-1900 you may be able to find what you are looking for at:http://www.jewishgen.org/jri-pl/jriplweb.htm
I found my paternal grandfather on this site and from this I've got my dad's family back to Mendel Popinski who was born in 1780.
My problem is in 20th century records as from my dad's family he was the only Holocaust survivor and as he never spoke about it I'm not even sure how many siblings he had or what their names were. This makes it very difficult to find out what happened to them.
Hope this helps.