I think the thing that angers many about the sentence being based on the fact that they were minors when they committed the crime is that for many years as adults they have continued to deny any responsibility for their actions and continued the suffering of his family.
The Lawrence family have given up 18 years of their lives to get this far and no doubt will give up more years still in the pursuit of justice for the other members of the gang. I can see how hard it must be to realise that the guilty may give up less.
I’d like to think that the 2 now inside will have it made known to them that they could be kept till they die if they don’t come forward with the names of the rest of the gang. may not be possible or legal but it would be worth planting the idea in their minds.