Swiderski, Pelechata - Genealogical search

I am looking for my late grandmother's family.

Klement/Clement Swiderski, wife Petronela Pelechata/Pelechato. My grandmother, (their daughter)Tekla, aka Kathleen, married George Benard in Montreal in 1925. Klement and Petronela had one child here, Jan or Yan, in 1914, but I have not been able to find them in the 1911 census. I suspect they arrived in Montreal between 1911 and 1914.

I believe Tekla and her siblings all took 'american' first names here. I remember a Great Uncle Peter, Great Aunt Frances, Great Aunt Mary, but there were more. Tekla/Kathleen died in 1971, well before I cared enough about my history to enquire. The family could be Polish or Ukranian, I'm not sure. Frances married a Gerry Derocher/Durocher/Desrocher and also lived in Montreal.

If anyone has any leads, or can point me to other possible sources to check, it is much appreciated.

The following are researching the Świderski name:
Swiderski -- POLAND > USA -- HppyGrl866@aol.com -- Jun/01
Swiderski -- Udrzyn & Łomża area -- joeflip@earthlink.net -- Feb/01
Swiderski -- Poznań > Pennsylvania, USA -- workintv@aol.com -- Feb/97
Swiderski; Świderski; Schwederski -- Kreiss Goldap, EAST PRUSSIA; now Gołdap, POLAND -- tedjeo@maroon.tc.umn.edu -- Nov/96