I raised a large family K”H and my children were all very well adjusted and loving to each other. There was no need to Patch or punish, above all I never raised my voice, always speaking calmly, (our neighbors could not stop admiring us they never heard yelling from our house). It is very important never praise or show accesively love and affection in front of the other children. This is very painful for a sibling to watch. Try it, you will see a tremendous difference.
Our children are all married by now and raise their own families, Each have their own Mazel, some are well off, others have less.
There is B”H no Machloikes or jealousy,no difference among sisters or sister-in-laws on the contrary they are always helping each other out, The main think is Daven to Hashem.
Good luck,