These are some family trees. The first gives you an idea of how the main royal noble houses came about in their descent from Edward III.
The Neville Family Tree
The Neville's originated from the Conquest, and steadily grew in power during the 13th and 14th centuries. This Family tree starts from Ralph Neville, the 1st Earl of Westmoreland. You can read a little more by going to the 'Major Families' page
The Percy family tree
The Percy family was threatened by the rise of the Nevilles. For many generations Percy and neville had worked together, and indeed continued to work together - the Percies remained related by marriage to the senior line, the Earls of Westmoreland, bit was Salisbury and Warwick's lines that now dominated the family. Once again, there's more in the 'Leading Families 1450' page, and the 'Leading Families 1471' page.