Thanks for the added info.
The 1900 Census lists their arrival year as 1894 and that they have been married for 6 years. John is listed as being born May 1871 and Castia in March 1870.
Their two sons were born in Pennsylvania with one additional child who died.
Simon Serandis is listed as a brother-in-law in the household which likely means Serandis is Castia's brother.
John and Castia are both listed as AL (Aliens)in the 1900 Census. What is their citizenship status in the other censuses?
Have you found them in the 1930 and 1940 censuses?
Also, when did they die? They have have completed Social security card applications which might list their birthplace.
What were the arrival years listed for them in the other censuses?
Sorry for all the questions but I just wanted to know what info you already had found.