The name De Breos (De Braose, or various other spellings) is one of the significant ones in the history of Swansea, and in the family line were several Williams. Some of these inherited the estates and some died young, making the counting of them somewhat controversial. The one we are interested in was born in 1261, referred to as either William III or William VII. Let us just call him William.
William took over many of the duties of running the estates before his father (another William) died, but he didn't inherit until 1291. Along with the estate, he inherited large debts, several law suits, and a profligate lifestyle. Consequently he was always looking for money, and not always particular about how he got it. The inheritance was large, and over the centuries the number of lands varied widely, depending on honours given and received, and sales made in an attempt to balance the books. In some cases land was forfeit due to the displeasure of the king, and in others land was given in recognition of service, particularly in war.
At the time of his inheritance, the main estates were Bramber (West Sussex) and Gower (South Wales), but William seems to have spent a lot of time in Gower, and rebuilt Oystermouth Castle in stone, which he preferred to live in, although Swansea Castle was the main seat of Gower. However, it is possible that Swansea Castle was in some disrepair, as the whole town was sacked and burned just over 50 years before, by Rhys ap Maredudd in a Welsh uprising.
By the time William inherited, his father had already sold off the north and south gates of the castle, and William himself sold some of the towers. He was able to do this because the castle became less important for military purposes by 1300, with the end of the Welsh wars. It was however, still the administrative centre and principal seat of the lordship. When he eventually worked on it, he built the 'new castle' in the south west corner of the original, and left the rest as part of the town.
William was married to Agnes and had one son (another William), and two daughters, Joan and Alina (named after his mother). Sadly, William (the son) and Joan died before him, and Alina was left as his heir. He did, in fact, make arrangements for her to inherit, but his “great unthrift”, as one writer put it, meant that her inheritance was far from certain.
To be fair, all barons had to raise men to fight for the king, at their own expense, and both William and his father had done so several times, and to great success. He served in Scotland many times, including the defeat of William Wallace, and at Bannockburn. He served in Flanders and elsewhere on the Continent. And also in West Wales against the Welsh, for the Marcher lands like Gower were part of England. William even had a huge siege engine, with all the men necessary to maintain, move and operate it, which was a key factor in winning the siege of Emlyn Castle, in the campaign against Rhys ap Maredudd in West Wales in 1288.