Hello and Thank You for using Just Answer. I am sorry to hear about the problems that your grand children are experiencing with their mom and her partner. You are in a difficult situation but at least your grand daughter can confide in you. The concerning aspects are what is really happening in that household behind closed doors. There may be mental abuse. You have already hinted about inappropriate touching.
A course of action that you may want to take is to call your local child abuse hotline. You can tell them..without giving your name...all about what you have witnessed and know about the relationship between your grand daughter and her mom and partner. They will lead you in the right direction to take based on your knowledge. If you decide to file a report, an investigation will proceed. This is a serious situation especially since your grand daughter had thoughts of suicide. There may be much more to the ordeal than you know.
Hope this helps and provides you with insight. Thanks!!!