I hate being the bearer of bad news, but your Romualdo Garza, b 1849, cannot be the same Romualdo Garza son of Eugenio Garza and Crisanta Laureles. That is, of course, unless you made a mistake on the birth year.
Here are a few records for you to consider.
Texas Marriages, 1837-1973 groom's name:Eugenio Garza bride's name:Crisanta Laureles marriage date:01 Jan 1876 marriage place:Starr, Texas indexing project (batch) number:M75268-3 system origin:Texas-EASy source film number:1016451
Note that the marriage of Eugenio and Crisanta is 27 years AFTER your Romualdo was born.
Here’s a death record on Romualdo Garza:
Texas Deaths, 1890-1976 name: Romualdo Garza death date: 08 Jul 1959 death place: Mcallen, Hidalgo, Texas gender: Male race: white death age: 77 years 5 months 1 day birth date: 07 Feb 1882 birthplace: Texas marital status: Married father's name: Eugenio Garza mother's name: Crisanta Laurel occupation: Ranch And Farm place of residence: McAllen, Hidalgo, Texas cemetery: City Cemetery burial place: Rio Grande City, Texas burial date: 09 Jul 1959 digital film number: 4165922
Again, note that Romualdo, son of Eugenio and Crisanta was born 1882 and not 1849.
Now for the information on the 1900 census of Starr County regarding Luis being born 1870:
If you look at the census, note that you will see that right below Luis (age 19, b 1870),is Romuhaldo (age 18, b 1882).If Luis had been born 1870, he would be 29 years instead of 19 and at least 8 years older than Romualdo.I believe the census taker wrote down the wrong birth year for Luis and should be 1881.Also note (again) that Romualdo (son of Eugenio & Crisanta) was born 1882 (coincides with his death record) and not 1849.