.Kids.us is one of those domain extensions that sounds like a good idea, but when you look at it a bit more closely you end up having more questions than answers. Essentially the domain extension was designed to be a safe internet space for “kid friendly” content, but the restrictions on registration were incredibly tight. How many .kids.us domains were registered? No idea, but it’s pretty safe to assume that the number was incredibly low.
In any case the US government, which runs the .us domain extension, has decided that .kids.us is to be shutdown. No new registrations will be processed after the end of this month and any existing domains will need to migrate to other extensions within the next 12 months.
Kevin goes into it all in more detail here.