Recently, my sister and her husband has problems in their marriage. For some reason, his family got really involved to the point that they made him choose sides. Long story short, everyone from his family stopped talking to everyone in our family, including the children. This is all manageable for us the grown-ups, but how do I explain to my poor innocent girls (ages 8 and 4) why their beloved friend (my sister's husband's niece, age 10) suddenly stopped talking to them? They really love her and will be pretty hurt, so I want to find words to explain that this is not their fault but I can't seem to be able to find a suitable explanation in my head.