It might be a good idea. I remember when our oldest son was 12, our neighbors had a 12 year old daughter. One night my husband was putting out trash and saw the 12 year old daughter sneak out of her bedroom window and get in a car with three boys at least one was old enough to drive, but they all looked at least 16. My husband told her dad.
At first the dad didn't want to believe it, but when he went into the bedroom she was gone and they had to go find her. If my husband hadn't seen it, they may not have found out, and who knows how long she could have continued that behavior and what could have happened to her.
Your sister and her husband might just want to keep an eye on what's going on for awhile, but as a parent, I'd want to know if my kid had a boyfriend or girlfriend sneaking into the house.
at 3:45 PM on Oct. 7, 2012