I believe these men are all from the same family. They were all found in Humboldt County 1900-1930 census. They lived in Pacific, Ferndale and Table Bluff. If you can confirm that they are father and sons, or add more info to what I have, please contact me at firstname.lastname@example.org
Martin MENG b. Feb 1851, DEN d. bef. 1930, Humboldt, CA. emmigrated 1880, m. abt 1873, Johanna b. Jul 1853, DEN
Andrew P. MENG b. Sep 1874, DEN m. abt 1896, CA, Hansene (Hansie) b. Dec 1876, DEN (children: Constance, Mamie, Curtis and Merton or Martin)
John P. MENG b. Jun 1876, GER or DEN m. abt 1898, Humboldt, CA, Martha b. Jul 1873, NOR or CA (children: June M., Olive G., Marvin P., Grant J.)
Johanna states in 1900 census that she has had 3 children and 3 living. I didn't find any other MENGs in the Humboldt County area, so maybe the other child was a girl or another son, left behind in Denmark or Germany.