Ethical Issue- Is this child abuse? Do I need to report this?

I've been working as an LVN with the same family (home health) for a little over a year now. This is pretty much my first case as a nurse and I think I made a BIG mistake getting too involved with the family that I work for.

My patient is a 27 month-old boy with one of the most complicated syndromes anyone could imagine (affecting almost every system in the body). I will call him Sam for this post. He has a trach, GT, has undergone open heart surgery, is moderately to profoundly deaf, wears a hearing aid, glasses, has yet to walk independently, and uses sign language to communicate (he knows and regularly uses almost 300 signs).

His mother insists on being with him at all times (she's a full time mom). I will call her Mary. Mary knows almost everything about his care and taught him most of his signs. When we first met, we clicked instantly and throughout the time I worked with her we became incredibly close. She also has another son, who is 9 months-old (I was there for the birth, at her request because we were so close).

The problem is that Mary absolutely hates her husband (the father of these boys, whom I will call Mike). Mike still loves her and believes marriage is forever, despite the physical and emotional abuse he takes from his wife; I have witnessed her verbally attack him dozens of times right in front of me (and Sam).

They recently went back to visit their families in the UK and while there, Mary hit her mother-in-law. When Mike and his mother tried to escape with the kids, Mary slashed her mother-in-law with her keys, grabbed Sam out of the car, and locked herself in the house with him. Mary's parent's managed to get Sam out of the house and take Mary and her other son into their care. Mike fled to his parent's home with Sam. A few days later, Mary shows up with her other son (sans formula, diapers, and adequate clothing for him) and says she wont leave without both boys. The cops say Sam needs to stay with his father.

Mike filed for divorce requesting custody of both boys two weeks ago, but I just discovered they've reconciled (because she realized she couldn't win custody... unbeknownst to Mike, who thinks she's back because she loves him.) The whole family will be back to the US next week. I am the only person in the US that knows what happened.

I wasn't there for any of this. I only know about this situation because I've become friends with Mike's sister.

Do I need to report this in the US after these incidents were already reported to police in the UK? There will be no question as to who reported them here AND I didn't actually witness any of this.

This is a nightmare and whatever comes from this situation will be a life lesson I will never forget.