Lafe Langford lauded Devin and the boy's sister for helping protect the other children.
Devin's mother Dawna Langford and two of her sons were also killed by the gunmen.
The brutal attack occurred on a highway in the border state of Sonora, where three carloads of Mormon relatives were fired on, and at least one vehicle burst into flames, officials said.
After his mother was shot in an ambush near the US-Mexico border, a 13-year-old boy hid his siblings and walked for about six hours to get help, his family said. "When he took too long to return, his nine-year-old sister left the remaining five to try again".
Her seven-month-old baby, Faith Langford, survived the attack. She was listed as missing for a while.
"They had to have known that it was women and children", he said.
"The first thing that came out of her mouth when she saw her uncles was, 'We have to go back". They were traveling from LaMora, located in Sonora, Mexico. All three mothers lost their lives in the slaughter. Rhonita returned to the religious community to change cars and when she left the other women followed as they were on their way to a family wedding in another town.
But shortly after leaving, all three cars were ambushed at different points by gunmen near Bavispe.
Devin quickly took charge, covering his siblings with branches to keep them safe while he went for help.
Rhonita Maria Miller, her twin infants Titus and Tiana, son Howard and daughter Krystal (above) were among nine U.S. citizens shot and burned in their SUVs Monday. This was the case on Monday and was reported on Tuesday by Kendra Lee Miller.
"All of a sudden, bullets just rained from above, from on top of a hill, down on top of them", Langford said.
"There were remains inside and outside of the vehicle".
One vehicle was shot until it exploded and caught on fire.
Christina Langford Johnson, 31, was also killed in a third vehicle.
Yet inside a torched auto riddled with bullet holes, a tiny sign of life emerged.
The victims include Christina Marie Langford Johnson, 29; Dawna Langford, 43; Trevor Langford, 11; and Rogan Langford, 2. She was gunned down.
Dozens of high-riding pickups and SUVS, many with US license plates from as far away as North Dakota, arrived in La Mora for the funeral, traveling over the dirt road where the attack occurred. All of the victims were apparently related to the extended LeBaron family in Chihuahua whose members have run afoul of the drug traffickers.
Some reports have tied the murders to the family's history of run-ins with the cartel, including the 2009 kidnapping of 16-year-old Eric LeBaron.
Miller said the family was told that if the bullet had gone a quarter of an inch deeper into Brixon's chest, he would have been killed.
"His jaw is actually broken. He's got fragments in his head", Miller stated. "He is actually in a more serious condition than they thought".
After seeing his mother and two brothers die, Devin walked about 14 miles to La Mora and relayed the "first news anyone had heard" of the attack, Miller said. "[They] are fairly composed", Miller stated. "Last night, Devin was in shock, a little bit confused and just exhausted after a awful, long day". "I think it was a miracle".
Officials confirm 3 women, 6 children die in northern Mexico attack; relatives say victims United States citizens.
"The violence and disregard for human life displayed by these criminal organisations is as barbaric and gruesome as any terrorist organisation we see around the globe". "It's incomprehensible, the evil".