My husband’s second great-grandfather on his father’s side, David THALER, was born on March 10, 1840, in Bayern, Germany to Johannis THALER and Maria Eva WEIGEL. David died August 1918 in San Luis Obispo, California, USA. I forget the exact details, but David THALER’s name is mentioned in one of the stories on a wall inside the Mission San Luis Obispo de Tolosa. He was one of the key helpful Caucasian men in the earlier days at the mission.
My husband’s second great-grandmother on his father’s side, Hannah A. BLAKE, was born on July 9, 1858, in California (possibly in Napa) to Ander (or Andrew Jackson) BLAKE (May 5, 1826-September 13, 1900) and Elizabeth (February 4, 1841-October 21, 1901). Hannah died January 4, 1919 in San Luis Obispo, California, USA.
Below is what can be found in the 1900 United States Census for this couple and their family. It shows that they had a six-year-old lodger whom I cannot figure out. He is not in the 1910 Census with David and Hannah and the name is not familiar to me.
Name: David Thaler
Age: 60
Birth Date: Mar 1840
Birthplace: Germany
Home in 1900: San Luis Obispo, San Luis Obispo, California
Race: White
Gender: Male
Immigration Year: 1857
Relation to Head of House: Head
Marital Status: Married
Spouse’s Name: Hannah A Thaler
Marriage Year: 1878
Years Married: 22
Father’s Birthplace: Germany
Mother’s Birthplace: Germany
Occupation: Chief, Fire Dept.
Household Members:
Name ~ Age ~ Birthplace (BP) ~ Father’s BP ~ Mother’s BP ~ Occupation
David Thaler ~ 60 ~ Germany ~ Germany ~ Germany ~ Chief, Fire Dept.
Hannah A. Thaler ~ 40 ~ California ~ Indiana ~ California ~ (blank) ~ 3 children all living
Josephine M. Thaler ~ 21 ~ California ~ Germany ~ California ~ Teacher
Arthur Thaler ~ 19 ~ California ~ Germany ~ California ~ Teamster
Fred E. Thaler ~ 11 ~ California ~ Germany ~ California ~ School (student)
Iowa Keyser ~ 6 ~ California ~ California ~ California ~ School (student) ~ LODGER
David and Hannah Thaler were the parents of Josephine M. THAYLER/THALER JOHNSON (1879-1975), who was the mother of Evelyn Iola JOHNSON PARKER (1908-1979), who was the mother of my father-in-law.
Digging For Ancestors 
Are there any others with last name Keyser in the area?
Not really close by, but I did notice that a few others on pages nearby also had one lodger each, but they were at least in their twenties. Their oldest child (who was still living with them at 21) was a school teacher, so it is possible that maybe the family took in the young boy temporarily because she knew of the need. Great question!