Dealing with other people's children when it comes to discipline can be tricky and a touchy subject. There are boundaries that should obviously never be crossed and with all the different parenting styles the task is even more difficult. Then toss in the fact that your input may not be welcome at all even if your child is involved, finding the correct way to intervene when needed can really take some talent.
Stepping in when you're with your friends and family is easier said than done. You'd think that it wouldn't be that big of a deal since you know how the child is normally handled. But what if you're dealing with a child that has virtually no discipline to speak of? They get away with out bursts, temper tantrums, outright disrespect to adults and do whatever they want. They always run the show because no one will do anything about it or there is always some excuse to not handle the situation.
I personally have been this situation many times with friends and family and I'll be honest, stepping in doesn't always go over so well. Every time that I have felt it was severely needed and it involved my child, I do not regret it or take it back. For instance, when someone else's child thinks it's okay to clock my child and the parent feels no need for intervention, I have a problem. Same goes for the opposite situation. I will not tolerate hands on fighting with the kids. There is no reason for it and it is our job as parents to teach our children how to properly handle themselves in a disagreement with others as well as punish the bad behavior to put a stop to it.
The last situation I was involved in where I had to step in with another person's child, mine was the one that got physical. To start, this is not normal behavior for her in the first place and was shocked that she had put her hands on this other little girl. However, I know this other child very well and has many behavior issues of her own. I immediately wondered what she had done to push my daughter to the point of hurting her.
Wanting the full story, and with her mother less than 5 feet away me and her daughter, I asked what had happened while looking over her arm that my daughter had scratched up pretty bad with her finger nails. She just stood there and ignored me. I asked several more times and explained to her that what my daughter did was not okay but I needed to know how everything went down so I could have a talk with my daughter and punish appropriately (I knew that they had been rough housing and we all know how that can get out of control quick). She continued to ignore me and her mother did not step in once to help the situation. After trying to get the story out of her one last time, she simply walked away from me and went to her mother to complain about the scratches. Her mom told her to just “get over it” and to go back in and play and that whatever made my daughter upset with her she'll get over it if she hasn't already, then went back to her conversation.

