Your grandfather's half brother would still be a "great-uncle" to you. and Mendez would be Marco's mother's last name , not his wife's. Do you record your family history on your computer? Do you have a genealogical program,like"Family Tree Maker"? Whenever you record a name on the program it puts the name in the correct location. Also, "Cyndi's List"cyndislist.comwill have a list such as that.
I am researching this family as my d-in-law is a Robles and I am making a book for the grandchildren. Unfortunately the family is extremely UNINTERESTED in this research so I am having to work very hard to find this info from folks like you. I have a great deal of information but connecting it is the issue. How old are you? I am 61 . Your age is important because it tells me which generation you are. Please don't be offended. I would like to speak to you sometime. I will give you my cell phone number if you wish the same. Thanks in advance, Pat Miers