I found a newspaper report from July 1901 regarding the conviction of Reuban Henry Plimmer. It states he had been married for 3 years and had 2 children. The article says that he was the brother of the famous boxer who from an 1896 article I believe was Billy Plimmer and Reuban was his trainer/bottle man. In 1901 Reuban's address is given as 89 High Street, Aston - labourer.
In December 1901 he is a private in 4th Royal Garrison Regiment in Aldershot - article about failing to pay maintenance for his wife Maria.
There are a few articles about Maria's antics in the Lichfield area in the early 1900s, seems she was quite a colourful character too.
I think Boxer Billy is in Sheffield too in 1911 and I also think it may be him with Bella in 1901 rather than Reuban (why would you give 2 sons born so close to each other such similar names - to confuse us genealogists no doubt

Pinetree
From a tree online the William you have b.1869 was Billy the boxer and Isabella's mother's maiden name was Horton!