Soulmagent--My heart goes out to you. Our family's dealt with a nutty set of "other" grandparents for seven years. First, they wanted to "force" our daughter into terminating her pregnancy because she's Asian and the father is white. The other grandmother actually had the audacity to set up a meeting with me and my daughter and then commenced to PRAY that she'd have the strength to end the pregnancy. I'm a very gentle person but I almost decked her. She then called an abortion clinic and pretended to be my daughter to set up an abortion. And she presents herself as a good Christian woman...Jeesh.
They make one poor choice after another--no car seat, no fence around the pool, heavy duty pain meds during the day while our girl watches movies, dog bites going untreated, letting our baby girl go with people they hardly know. It drives us to distraction. I literally have to start every single day calming my daughter down. She's since married and has a wonderful husband and they have custody of the child but the grandparents have her for two nights a month and something always goes wrong--always. No one says that they don't love the child, they just won't grow up and be responsible.
You and the other posters are absolutely right--just because someone is a relative and even loves the child, does NOT mean they are safe.