"In many ways, those are the children and families who need us the most," said Dr. Mark Kline, physician-in-chief at Texas Children's Hospital.
Kline said more of them are uninsured and as a result, have greater health risks.
Kline, who is also chief of the pediatrics department at the Baylor College of Medicine, said its alliance in San Antonio will serve local families, as well South Texas and Mexico.
Kline said its partnership will provide the region "world class pediatric care."
Some already is underway, according to a spokesperson at Children's Hospital of San Antonio, even as it undergoes reconstruction at its longtime location as the Christus Santa Rosa downtown hospital.
Kline said the new hospital opening late next year, will be smaller than the sprawling Texas Children's Hospital in downtown Houston.
However, he said they want to avoid "two tiers of quality."
Kline said their young patients also could benefit from cutting edge research.
"Texas Children's and Baylor College of Medicine have a special niche in pediatric research," Kline said.
He said more is on-going "than at every other institution in the state of Texas combined."
Kline said having been raised in San Antonio himself, he commends Christus Santa Rosa for its long history of service to the community.
"I think the partnership is going to take it to the next level," Kline said.