I would like to put a quick disclaimer on this pet peeve - It is not my peeve, but was suggested to me by my old cronie and fellow CSU Ram, Tricia Fry. I'm going to attempt to share it, because when Tricia told me about this peeve, I instantly agreed. She is so right. The problem is when people casually drop the "my" when talking about a family member. This means that someone whose mother you have never met says things to you like, "Mom is coming over to my house for dinner tonight." or "Dad always has to have green bean casserole at Thanksgiving."
Just this very method of communication with those outside of your family, who are not in fact related to these people, is TMI. It's not my Grandma, so please don't refer to her in the familiar with me. "My Grandma is coming into town." is appropriate. "Grandma is coming into town." is not. Did I miss something? Are you talking about my grandma? I guess you didn't get the memo that she passed away.
Please, when it comes to dropping the "my", keep it in the family.