Just because the English name is "Anna" does not mean they had the
same name! You need to compare the Hebrew/Yiddish (or Ladino if
Sephardic) to understand the real names. There are many many many
examples of brothers coming to US and winding up with the same
partially transliterated English name. (examples: Hirsch and Hillel
both going to Harry etc. etc.) Understand that for Jews the real
name was the Jewish name, which was then usually translated to other languages -- only with American assimilation did this business of
transliteration, or transliteration using only intial first letter --
get going. Also, since Ashekenzaim named after dead they wanted to
remember, no reason could not have happened with brothers. (would
not seem at all strange to a family who would be knowledgeable about
levirate marraige and rabbinic ramifications thereto)

Jonina Duker