Overheard: Goober Edition

A few weeks ago, while working on the guest list for our baby shower (this Saturday!):

Shrike: I don't know about inviting my mom, honey. 

Whozat: Why not?!?

Shrike: Well, it just seems kind of pushy, don't you think? 

A message on our answering machine today: 

Shrike's Sister: Hey, I might have told you already, but if not, I just wanted to ask you to please call and let me know when Whozat goes into labor. 

What the fuck? 

Do these people not realize that they are related to each other?