"Some owners even chose to be buried at the pet cemetery, since they could not be buried alongside their pets at human cemeteries..."

"'It was so important for some people that they stay together that they decided to be interred in a pet cemetery.'"

From "The Most Popular Pet Name of the Century (Maybe)/A survey of tombstones from the oldest continually operating pet cemetery in the U.S. reveals a passion for 'Princess'" (NYT). 

The quote is from Allison C. Meier, "a writer and licensed New York City sightseeing guide who gives tours of the city’s cemeteries." 

Another quote from Meier: "The way that people refer to their pets changes. On a lot of old dog graves, they call them a gentleman — like, 'He’s a great gentleman. He lived like a gentleman.'"

The original meaning of "gentleman" is "A man of gentle birth, or having the same heraldic status as those of gentle birth; properly, one who is entitled to bear arms, though not ranking among the nobility... but also applied to a person of distinction without precise definition of rank" (OED).

Later — and by later, I mean in the 16th century — it became "A man of superior position in society, or having the habits of life indicative of this; often, one whose means enable him to live in easy circumstances without engaging in trade, a man of money and leisure. In recent use often employed (esp. in ‘this gentleman’) as a more courteous synonym for ‘man’, without regard to the social rank of the person referred to." And apparently, without regard to the species of the being referred to.

Are you teaching your sons to be gentlemen (with or without the use of that word)? Are you teaching your dogs?