What article if any should I use in the sentences below?
I have -/a/the dog Rex.
I have -/a/the brother Sam.
I surmise that in the second case there is no need for an article. Thank you for your help in advance!
In I have Rex or I have Sam, you don't use articles.
If you're using the word "dog" or "brother", you must use articles.
"I have a brother, Sam" means you have a brother called Sam (or that you are speaking to someone called Sam and telling him that you have a brother).
"I have a dog, Rex" means you have a dog called Rex.
"I have the dog, Rex" means that you have a particular dog that you probably expect the other person to have heard about previously, and that it's called Rex.
