Most of what I have to offer in this posting is based upon my own experiences over the years.
Parents should not have more children than they can: physically, financially, and emotionally support. There are of course times when a calamity or accident occurs and others need to step in and help. Sometimes older siblings end up raising younger siblings.. It is natural for older siblings to help in the home and to help with younger siblings; but problems often arise when an older sibling is required or even put into a position to discipline their own siblings. This is not their role except in the case of an immediate emergency, incapacity ,or death of the parent(s).