The parents should take care of their children so they could easily build bonds together wether good or bad situation. as uncle to the children, you can do well to assist the parents financially by passing the children the school fees when the need arises, send them money once once for upkeep, and a whole lot more. But outrightly taking the kids away from their parents is what I wouldn't endorse, nobody is in a better place to take care of a child than his parent. as a relative your support will be notice by both the parents and the children if you assist them.
You have made a captivating argument I wish to agree with for a relative who passionately wants to assist a brother man will want to extend the help regardless the child still lives with the biological parent. On the contrary to your compelling position I'm having it on a different thought that this approach of sending the child fees to the parent will not last long relative to when the child living with the relative. And this is not only about paying the child school fees but taking care of the whole well-being beyond her school fees which is part of the burden bore by the parent.