The Problem with Medieval Heiresses
Heiresses passed on properties and, if they were sole heiresses, they could even pass on titles.
This was not a problem if their husband was not already handsomely endowed and if he did not have any title. The husband took over what had been done by the father of his bride.
But the problem came when the husband and wife were both handsomely endowed and both had titles. The resulting union was very rich and very powerful and in medieval times when most senior peers had their own private fighting forces, these forces could become enormous.
The classic case of this was the Neville family. On the one hand Ralph Neville, first earl of Westmorland and who married for his second wife the half sister of the Henry IV, managed to acquire four peerages, two earls and two barons for his four sons of this marriage; the Westmorland title went through his heir of his first marriage. On the other hand his grandson Neville the Kingmaker, acquired two of the largest earldoms, Salisbury and Warwick, to himself. This concentration of power in single people and a single family was too much for the kings to handle. The medieval practice had been divide and rule; the sovereign had to be significantly more powerful than his subject tenants-in-chief. It was not surprising that this led, in part, to the Wars of the Roses.
The Tudors realised this problem and put a stop to accumulating titles and property by marrying heiresses. With the death of most of the old governing families, they were able to create new titles with new rules. The primary new rule was that new titles were to descend in the male line and not through females. With a few very special exceptions, this has been followed to the end of the days of hereditary peerages.