I'm just getting started searching for this family in Wexford, Ireland. The only reference I have to Wexford is on Martin MITHEN's death certificate. It does not specify the town of county, merely "Wexford, Ireland." Please contact me if you have more info. Here's what I know so far:
John and Nellie MITHEN. John b. Wexford, Ireland. Known son:
Name: Martin MITHEN
Birth: 4 Mar 1850 Wexford, Ireland 
Death: 27 Jun 1937 Rancho Los Amigos, Hondo, Los Angeles, CA 
Burial: 30 Jun 1937 Calvary Cemetery, Los Angeles, Los Angeles, CA 
Occupation: Hostler, Farmer
Father: John MITHEN
"Mithen's Pampas Ranch
Martin Mithen, at Carpinteria, carries on one of the most unique industries in Southern California, being nothing more nor less than a producer of vegetable feathers, better known as pampas grass plumes--the flower stalk of a species of grass whose habitat was the pampas of South America. Originally transplanted to Southern California as an ornamental shrub, it was soon discovered that they made beautiful interior decorations, and the plumes, now well known throughout the civilized world, were soon in great demand.
The pampas grass, that, in full growth resembles a large haycock with a mass of gigantic feathers stuck in it, took kindly to the soil of this section, and, for a while single plumes sold as high as 10 cents each. Mr. Mithen, having some wet land, especially adapted to the raising of pampas grass, set out six acres that, year in and year our, have brought him more money than any crop he has ever raised. Last year, from the six acres, he harvested 150,000 plumes, which sold for $11 per thousand.
Martin Mithen is a native of Ireland, 50 years of age. Coming here in the early days, he realized the value of the land for agricultural purposes and purchased 340 acres from Jacob Wilson, portions of which he has disposed of, from time to time, to advantage. He has left a fine homestead, with a handsome dwelling, good barns, etc., and plenty of stock. Besides pampas plumes, he cultivates citrus and deciduous fruits, hay and lima beans." 
Occupation: farmer. Last worked as a farmer in 1925. Spent 60 years in this occupation. Informant: Records of Rancho Los Amigos (LA County poor farm). Length of residence in city: 11 mos, 21 days. 57 years in CA; 63 years in U.S. Widowed. Funeral Director: J. A. Coleman Mortuary, Los Angeles, CA. 
Spouse: Alice LACEY
Birth: ca Mar 1850 Ireland
Death: 13 Oct 1924 Van Nuys, Los Angeles County, CA 
Burial: 14 Oct 1924 Calvary Cemetery, Los Angeles, Los Angeles, CA 
Father: James LACEY
Mother: Catherine BROWN
Informant on death certificate: Martin Mithen of San Fernando. Funeral director: Will E. Noble, San Fernando. Physician: Dr. E. Thompson, Burbank, CA. 
1 F: Mary F. MITHEN
Birth: 27 Mar 1876 San Francisco, San Francisco, CA
Death: 2 Dec 1926 10720 S. Main St. Los Angeles, Los Angeles County, CA 
Burial: 7 Dec 1926 Valhalla Cemetery, Los Angeles, Los Angeles, CA 
Spouse: Edward SHARKEY
2 M: James MITHEN
Birth: 9 Nov 1877 Ca
Death: 15 Apr 1886 Santa Barbara County, CA
Burial: Carpenteria, Santa Barbara, CA
3 F: Alice MITHEN
Birth: Aug 1880 CA
Death: 6 Oct 1948 Los Angeles County, CA 
4 M: William MITHEN
Birth: Dec 1882 CA
Death: 24 Jan 1960 Del Puerto Hospital, Stanislaus County, CA , 
Burial: Del Puerto Cemetery 
Spouse: Marguerite (Margaret) M. PAWSON/BAWSON
Spouse: Alta Mae SAGER
5 M: Laurance MITHEN
Birth: Jul 1884 CA
Death: 20 Apr 1886 Santa Barbara County, CA
Burial: Carpenteria, Santa Barbara, CA
6 F: Katherine "Kittie" MITHEN
Birth: 14 Oct 1886 CA 
Death: 12 Nov 1962 Rosemead, Los Angeles County, CA 
Burial: 16 Nov 1962 El Monte Cemetery, Rosemead, Los Angeles, CA 
Spouse: Unknown DUDLEY
7 F: Nellie MITHEN
Birth: 20 Dec 1890 CA
Death: 18 May 1978 Monterey Park, Los Angeles County, CA
Burial: 23 May 1978 Savannah Cemetery, Rosemead, Los Angeles, CA
Spouse: Unknown STENGEL
1. State of CA death certificate for Martin Mithen.
2. Summerland Advance Courier.Southern Santa Barbara County and its Resources.1900.
3. State of CA death certificate for Alice Mithen.
4. State of CA death certificate for Mary F. Mithen.
5. “California Death Records,” http://userdb.rootsweb.com/ca/deathhttp://userdb.rootsweb.com/ca/death, 1 June 2000.
6. “William Mithen Obituary,” Stanislaus County, 25 Jan 1960, newspaper.
7. State of CA death certificate for Katherine M. Dudley.