In the book "C. Montgomery Burns' Handbook of World Domination", he is named "Colonel Wainwright Montgomery Burns" and has his "The Color Yellow" appearance, confirming that Wainwright, Colonel Burns and the shadowy figure that is seen adopting Charles as his own son in Rosebud are all indeed the same character.
Wainwright Montgomery Burns was born in the 1800s to the Burns family. Due to his upper-class upbringing, Wainwright grew to be a racist and villainous man. His unnamed assistant, who was shown in his manor house, is possibly an ancestor to Waylon Smithers. Wainwright was the inspiration for Harriet Beecher Stowe's character Simon Legree. She was later asked to tone down the character. In 1860, he owned a large plantation and also held a slave named Virgil who is directly related to Homer Simpson and his family. However, when Virgil was freed by the abolitionist Simpson family, Wainwright (known at the time as Colonel Burns) tracked him down to Hiram Simpson's cottage. He bribed Hiram with a pair of new shoes, and found Virgil in the tulip shed. However, Virgil was protected by Mabel Simpson. He was then threatened at gunpoint that if Colonel Burns ever crossed their ranch again, she would shoot him. A shaken Burns walked away the scene. 
Later on (possibly in 1895), Wainwright would forcibly adopt his grandson, Charles Burns, to be a greedy, heartless man like himself. 
In 1909, he took young Charles on a tour to his atom mill in Springfield.
It is heavily hinted in "Double, Double, Boy in Trouble" that the reason for Wainwright to have specifically chosen Charles as his heir was due to him being left as the oldest of the Burns children, since his 10 older siblings had all died, the family fortune, according to Charles, "ended up smiling on him", leaving Clifford and Daphne with only their youngest son, George Burns.
It has also been theorized that Wainwright owned shares in a business called "Confederated Slave-Holdings", which he passed on to his grandson. This would make sense, since Wainwright was a slave owner during the 1860s.
- Episode – "Last Exit to Springfield"
- Episode – "Rosebud" (non-speaking role)(as a shadow)
- Episode – "The Color Yellow"
- Book – The Simpsons Uncensored Family Album
- Book – C. Montgomery Burns' Handbook of World Domination