I suppose that it's different for a "worldly" man who enters the Kingdom Hall and eventually becomes a brother. As a study, I called adults by their first name and it stuck with me after becoming a "brother." Oh, there were those elderly ones who got called Brother Smith or Sister Harris, but it never seemed right to me.
I would be at a door with a nervous sister who would say at a door, "Hello, my name is Sheila and this is Brother OTWO." It must have screamed "CULT" to the woman at the door.