The system run by the O’Neills was highly oppressive by the people at the top. If you were at the top you could do very much what you liked, but you would be subject to the fact that your brothers and cousins and all had much the same ambitions. This is the weakness of the Gaelic system was defective mechanisms of succession so that the ruler would always be opposed by some of his own kinsmen unless he was exceptionally strong and had an exceptionally long reign so he could exclude them.

And he would be opposed by his own kinsmen who would feel that they had as much right to be ruler as he did; and of course these families proliferated to an incredible extent because they were in practice polygamous having a multitude of wives (in practice if not in theory) and because the illegitimate were admitted to a full share on par under native Irish law - they were admitted to full rights, they were not discriminated against as elsewhere, and of course in any lineage society where power depends on being born into a ruling lineage, just as in African societies, a woman maximises the opportunities for her children by having them fathered by a member of the dominant lineage.

So the O’Neills for instance, descendants of Owen O’Neill, (we haven’t a full list of his sons but he had about 15) but they multiplied as happened with every other Irish lineage and of course they pushed out the people, the existing landowners, they moved in on them and gradually displaced them, so that by the 1520s you have branches of the O’Neills established in all the outlying regions of Tyrone. But this establishment of branches of a ruling lineage is not a source of strength to the central ruler but of weakness, because whereas the former local chieftainly families who had been displaced would accept that they were his subjects and that he was ultimately over all, all these people would claim that they had as much right to be ruler as he was.