The attack occurred on the 800 block of North Granger Avenue.
Police said the siblings and their parents were visiting a family friend in San Bernardino from the Rialto area when the incident occured.
The victims, ages one and two were playing in the back yard of a residence when their family friend's dog savagely attacked the two-year-old in the face.
While the parents were rescuing their two-year-old, the 8-year-old pit bull bit and attacked the one-year-old.
Timothy Deremiah witnessed the savage attack.
"The pit bull bit his face and then they were trying to get him off of him and then the little baby got bit too cause it went to the little baby and then back to the boy," said Deremiah.
Both victims were bandaged and transported to a local hospital for serious but non-life threatening injuries. Both young children received stitches on their cheeks and were then released from the hospital.
The dog has been quarantined by San Bernardino City Animal Control. But authorities said the dog will not be euthanized because no crime was committed.
According to San Bernardino police Lt. Paul Williams, the children have played with the pit bull in the past.
"It would be a crime if hypothetically you were walking your dog down the street and you were agitating your dog to bite someone or the children were playing in the street, your dog was in the yard and you allowed your dog to exit knowing that that dog has the potency or the possibility of commiting an injury," said Williams.
The pit bull will remain at the animal shelter for the next 10 days as officials monitor its behavior. If the pit bull shows no signs of agression, it will be allowed to go home with its owners as long as they show proof of vaccinations and licensing.
The incident is the second pit bull attack in San Bernardino County this week.
On Sunday, a 74-year-old woman was attacked by a pit bull. Responding officers attempted to apprehend the pit bull but the dog allegedly attacked them as well. Officers were reportedly forced to shoot the dog.