I am strongly against any profile being added for a recently deceased child who died under age, however they died, without the clear agreement of someone in the close family. To me this is not primarily a matter of the legal situation, but of ethics and sensitivity. I ask myself how I would feel if, as a parent, I stumbled across a profile of a child of mine who had died: I know I would be shocked. Some parents may welcome such profiles as recognition of their child: others will have similar feelings to what I would have.
Where children have died gruesomely as a result of a crime, the sensitivities are even greater. Grief in those circumstances usually takes years to come to terms with, if the parents ever do come to terms with it. If a profile relies on newspaper reports or what is on another website, the information about how the child died may not be entirely accurate. Relatives of both victim and the criminal may be named who are still living, which does raise legal issues about privacy on top of further issues of sensitivity. Details of the death may be unsuitable reading for younger website visitors.
In terms of WikiTree privacy rules, even a living criminal has a right to privacy, however much we abhor what they did. Some convictions are unsound. There is a long history of convictions being overturned, quite often years later.
So if we must retain these profiles, my firm view is that they should be private, and preferably unlisted, with a Project managing them. But Unlisted is not currently an option for non-living people - see https://www.wikitree.com/wiki/Help:Privacy#Unlisted.
i would want myself to discourage the creation of further profiles like these.