Langdon, Rowe

I'm looking for information on my mother's father's family. He came to the states around 1900. One of his brothers was born in Barrow-In-Furness, Cumbria on 2 Sept 1888..his name was Alfred Archer Langdon but know to my mother as Uncle Fred. It hasn't been until recently we have just found information on our Langdon line. The problem though is that they moved a great deal and finding everyone's birth place has become a challenge. We have yet to find their parents marriage certificate. Their parents were William Thomas Langdon (b. 1856 Pengilly, Cornwall - death "total mystery&quotand Eliza Rowe (b. 22/24? August 1860 St Just Cornwall). I've already been in touch with many people trying to find the marriage certifcate there in Cornwall, but none to find. The family were living in Brotton, Yorkshire in 1881 & 1882-?? because I found them on the census / same address on my grandfather's (Richard Langdon) birth certificate in 1882.
The rest of the siblings were William "Tom" Thomas Langdon Jr. b. @ 1884., Samuel Langdon b. @ 1886., and only sister Ethel Annette May Langdon b. 30 Aug 1894. All the children and their mother died in California. We think their mother was widowed before 1900 when she came to the states.
I would appreciate any information concerning this family. Many thanks