Hi Mona! Here is a family tree provided by suprlinda from Silvertown Blues Forum, which may be helpful:
Michael (Mihaly) Knopfler
m. Maria
Jozef Knopfler
b. about April 24, 1874, Budapest, Hungary
d. New Bedford, Massachusetts
m. Selma Freuder
daughter of Elchanan (Elkan) Freuder and Julie (Jentel) Stern
Elkan b. 1818, Vienna, Austria
d. December 13, 1906 Deutschkreutz, Burganland, Austria
Julie b. February 1, 1836 in Papa, Hungary
d. January 26, 1915, Vienna, Austria
Alfred Knopfler
Erwin Knopfler
b. December 2, 1908, Miskolc, Hungary
d. 1993, London, Greater London, UK
m. Louisa Mary
Children as we know them, and perhaps 2 that died, as well (another David and another Ruth)
Marcus Knopfler
b. Miskolc
Olga Knopfler
It seems that Freuder is a surname from one of the ancestors - maybe that is where Mark's middle name comes from. Perhaps Austrian?