I wonder if you know of a Soledad Arellano? She married an American, Albert J. Kountz, maybe in the 1880s. They made a few trips back to Pennsylvania in the 1900s. Their children were born in Guadalajara, Jalisco. That is according to later border crossings, but I haven't found church or other good sources to confirm this.
George J. Kountz Arellano
Carolina Virginia Kountz Arellano, b. 1893
Augustin Kountz Arellano b. 1898
Catalina K. Arellano b. 1900
Maria E. Kountz Arellano
A newspaper article said that the father, Albert J. Kountz from Pennsylvania, went to Mexico after the U.S. Civil War and married Dona Soledad Arellano. Albert died about 1910.
George J. served in the Mexican Revolution in 1914 and died.
Albert J. Kountz had interests in the Mina Dos Estrellos and oil, too.
The family has been reported to have been in Tampico; Guadalajara, Jalisco; and later in Monterrey, Nuevo Leona. As I am working on this family I will let you know if I see anything that might be your Arellano family.
Laura