Josh, I didn't know that you came to Texas this past summer. If you had come near the Houston area, you could've seen my dad and talked to him.
I spoke with my dad this morning, and you are correct about that; your great-grandfather and my grandfather are in fact brothers. They were three brothers (Onofre, Juan, Modesto) and a sister (Lupe).
When I mentioned your grandmother's name to my dad, he said that she is his cousin. He said that he was very close with her and her brother, Miguel, back when they all lived in San Jeronimo, Copan; a village near Santa Rosa de Copan.
My dad didn't know that she was still alive; he was very happy to know that.
My dad mentioned Zacapa, Guatemala, and also said that some relatives also live in Chiquimula, Guatemala, but he does not know them.
As for Honduras (if you go looking for some relatives), we have relatives in San Pedro Sula: Rubenia Jordan and some of her children; Rodolfo Aranda and his children; Rodolfo's brother, Toño Aranda; and also a sister of Rodolfo. In Azacualpa, Santa Barbara we have, Dolores Jordan (most of her children's last name is Arita), Concepcion Jordan and children (not sure about their last names). In Copan Ruinas and/or La Jigua, Copan, we have relatives whose last name is Galvan (my dad mentioned a Cristobal Galvan who was his dad's cousin, although not sure where he fits in the picture). In El Paraiso, Copan we have Lupe's children whose last name is Pinto.
I'll e-mail you some sort of family tree that I've been able to make with the info my dad provided.