Start with what you know. That might be the obituaries of your parents or grandparents. Then work your way backwards in time using the Census records.
I didn't find any of these family members in Goliad Co. but you didn't say where they were born. If you're not familiar with genealogy, you might want to join your local genealogical society. Most societies will allow you to attend meetings without joining and you can ask questions. Successful Searching!