What is a Tejanos?
Basically, when Texas became a Republic, most Mexicans who were living there were loyal to the government of Mexico and left.
The Texas loyalists who stayed were known as Tejanos.
Bexar County, TX is something like 75% Tejano and many of them still keep in touch with and visit their Mexican relatives, just like many New Yorkers, Vermonters and Mainers keep in touch with their Quebecois relatives over the Canadian border.