Here's a difficult one...I am boarding a 3 hour domestic flight (am CC) and am confronted with 6 UM's. All have seats at the back of the plane and together, except 1 who in seated in 6C. Of course I questioned this then noticed the comment on the boarding pass "do not change seats". I thought this was odd and when I took this little guy to 6C he appeared scared and felt alone. There was a male in the next seat. I asked him if he wanted to sit there and he said no. I asked if he would like to sit at the back with the rest of the kids and thats what he wanted. Without even getting permission from the Purser or Captain I immediatedy took him to the back and moved a single pax into his seat at row 6. I know I should have asked permission to move pax but I felt this was a valid reason. Why on earth would a father book his child in a seat and say "do not change seats" and why the hell was this allowed by ground staff? We as cabin crew are becoming more and more responsible for not only our jobs but for looking out for the welfare of children. Enough is enough, we don't need grief if your child is abused or assaulted under our care. Travel with your kid, not post them around the country like a commodity.