Why should adults with kids get more basic income?
This is a question that shows a particular perspective in the very way it's framed. What about this question instead: "Why should kids get basic incomes too, and not just adults?" They might look like they are basically the same, but they contain different viewpoints. Here's the deal.
"Why should adults with kids get more basic income?" - The question of child allowances
There are multiple ways of going about a basic income. Some prefer it only go to adults. Some prefer it be equal for everyone, kids included. This is the argument to give a partial basic income to kids.