I realize it has been a very long time since you posted your note about your great-grandfather and his brother. However, I just ran across a letter that the brother, the priest, may have written to my husband's grandmother. I'm wondering if this Father Dan E. Reilly might be your great-grandfather's brother, and would like to get in touch with you.
You can see the previous two parts on the preceding two days links.
I realize you mentioned you don't know anything about your great-grandfather's brother, other than that he was a priest in Chicago, but I'd like to know if there is any possibility that this letter might have been from him. Do you think the dates match?