Even _I_ mistake one for another.
What usually happens is I call the Husband on his cell. He doesn't answer. I try his office. No answer. I call home and a male voice answers. Thinking that it's the husband, I'll start chatting. A good while into the conversation, he'll say something that makes me suddenly realize it's the Brother-In-Law... like "Did you want to talk to Will?"
And I'm in a mad panic trying to think if I've said something COMPLETELY RETARDED >_<
I should maybe warn the Brother-In-Law's girlfriend about this. MAKE SURE YOU HAVE THE RIGHT GUY BEFORE YOU START BLATHERING.