I am Rob Hoonan - I have lived here in the islands sonce the seventies.
I have found a story of the early pioneer missions in Texas which states that any history of cattle in Texas "must include information about the importance of cattle to the Spanish Colonial economy. With this in mind, I went searching for that particular piece of the Texas mission story. In Mary Ann Hoonan Guerra's pamphlet called "The Missions of San Antonio," I learned some interesting facts about the first cattle in this part of the world. According to Ms. Guerra, cattle came in 1519 from Spain to the area of Mexico along with Herman Cortez and his armies."
Try this name in a search site such as GOOGLE and you will find out about this Mary Anne Hoonan.
I am curious to learn if I am related to you also.