Bit Of Brother Bother

(My brother is a math teacher and his students call him Mr. [Our Last Name]. I am visiting one day and he is running a little bit late, so I am waiting for him in the classroom. The students are confused because I had introduced myself as Mr. [Our Last Name]. My brother walks in.)

Students: “Hi, Mr. [Our Last Name]. Who is this?”

Brother: “This is Mr. [Our Last Name].”

Me: “That’s right, Mr. [Our Last Name].”

Brother: “I’m glad you agree, Mr. [Our Last Name].”

Student #1: “What? Are you guys married or something?”

Brother: “No, but our parents are.”

Student #2: “Wait, isn’t that like, incest, or something?”

(At this point, we were laughing too hard to explain.)