Is it right for me to discipline husband's nieces & nephew?

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Here is the background. My husband is the youngest. His eldest brother died over 10 years ago leaving a wife and 3 kids. For some reason, the woman (wife) seeks help from my husband's family (and ours) and doesn't ask for help from her side. Naturally, my in-laws ended up taking her and her family in because she refuses to work (until very recently) and thus can't afford to raise her family financially anymore. Even the responsibility of disciplining her children has been relegated to my father-in-law. The issue is, my husband's nieces & nephew keep making the same mistakes to the point that my father-in-law has repeatedly blown up and threatened to move them out of his house. The children are already in their teens and twenties. If they move out of the house, there is a possibility that they will try to convince my husband to take them in or to give them financial support. We have 2 kids of our own! Plus, they keep insisting that my husband provide a fatherly figure to these children. The children have no appreciation of how fortunate they are to still be provided for despite their lack of finances. They are on scholarship but they don't care if their grades don't make the requirement. They ask for extravagances before making sure their needs are met. It has come to a point that it affects our family because they often expect my husband to come to the rescue whether it is paying for their bills, buying them shoes, or even mediating with their school to take them in again. It is crazy. And when they talk to me about their discipline methods, I don't entirely agree. I would like to give my two cents to these kids and make them realize how fortunate they are but I am afraid I will look too meddlesome. At what point can I intervene? Or do I have no place in it at all?