Just imagine that a woman has about 10 children, then forced them to have about 5 grandchildren per child. Now she has a gang. And all of that only because she wants to have full control over the neighborhood /s
You make it sound like bad to have a family gang.
It has so many uses, great for ilegal stuff, great for polítics, great for business, it is all benefits of controlling up to certain point a large group of people and having a strong link with them.