Jaya Ailani Trevino is the child who went missing. The Bexar County Sheriff's Office described the girl as a white female, 3 feet tall, 26 pounds, with brown hair and brown eyes.
She was last seen wearing a pink T-shirt with pink and purple lettering "Big Sister" on it and a Pampers diaper.
Jaya may be with 33-year-old Juan Trevino, who is described as 5'7", 180 pounds, with brown hair and brown eyes.
He was last seen wearing a white cap, black jacket, a blue Nike T-shirt, blue jeans and white shoes.
Authorities believe the suspect is driving a black 2014 Nissan Sentra with Texas license plate "MKS1273."
Law enforcement officials believe the girl is in grave or immediate danger.
Anyone with information on the girl's whereabouts is urged to call the sheriff's office at 210-335-4630.