OKLAHOMA CITY - Oklahoma City detectives have arrested a Tulsa dentist in connection with the death of 19-month-old Lincoln Lewis. 

Police confirm they have arrested 35-year-old Bert Franklin. Tulsa police said he is dating Lincoln's mother. And News 9 has also learned, Franklin is married and has four children of his own.

According to the family, baby Lincoln died on Monday, July 18, after suffering a head injury.

Facebook posts show Lincoln was born three months premature and his mother referred to him as "my sweet miracle babe".

News 9 crews first met Lincoln and his mother Roxanne last November, after he was given a precious gift from a local artist who helped personalize his cranial molding helmet with her creative flair.

Despite the medical challenges, the little boy seemed to be growing and thriving. And then news of his untimely death started flooding social media.

On Monday, July 18, Lincoln's biological father posted this on his Facebook page:

“My boy fought so hard these past 18 months to overcome countless problems. But two evenings ago he was struck in the head, cracking his skull and causing a massive brain injury. He has been robbed of a wonderful, long life."

He goes on to say "God bless you little Linc, you were so loved and we will see you soon."

According to a police report, the child was taken to Mercy Hospital in Oklahoma City by his mother.

She told police Lincoln had fallen down three carpeted steps onto a landing on Friday. She said he hit the back of his head against a wall.

According to the report, the mother told the officer, "I've seen him have some spills and tumbles, but the small tumble down three carpeted steps wasn't bad."

Lincoln was flown to a Tulsa hospital for treatment where he later passed away. The medical examiner's office confirmed the autopsy had been completed but the cause and manner of death are still pending.

News 9 talked with Lincoln's mother by phone, but she was too emotional to go on camera.

Lincoln's funeral has been scheduled for this Saturday, July 23, at Christ the King Catholic Church.

A GoFundMe Page has been created to help raise money for the baby's funeral. Friends who created the page have already raised thousands of dollars to help the mother of Lincoln Henry Lewis, who is grieving the loss of her precious baby boy.