Count Thomas III called Thomas of Savoy or de Savoie, was the lord of Piedmont

Lord of Piedmont

The lordship, later principality of Piedmont was originally an appanage of the Savoyard county and as such its lords were members of the Savoy-Achaea branch of that illustrious house. The title was inherited by the elder branch of the dynasty in 1418, at about which time Savoy was elevated to...

 and a claimant to the county of Savoy

County of Savoy

The Counts of Savoy emerged, along with the free communes of Switzerland, from the collapse of the Burgundian Kingdom of Arles in the 11th century....

 from 1268.

He was the eldest son of Thomas II of Savoy and Beatrice di Fieschi, niece of Pope Innocent IV

Pope Innocent IV

Pope Innocent IV , born Sinibaldo Fieschi, was pope from June 25, 1243 until his death in 1254.-Early life:...

.

Upon the death of his father, Thomas became Count in his paternal estates in Piedmont.

When his first cousin Boniface, Count of Savoy died in 1263, the 15-year-old Thomas regarded himself as the successor of the deceased, and claimed the county and the headship of the house. However, his late father's younger brother Peter of Savoy

Peter of Savoy, Earl of Richmond

Peter II , called the Little Charlemagne, was the Count of Savoy from 1263 until his death. He built the Savoy Palace in London....

, a sonless nobleman who had resided in England for much of his life, was recognized as count. After Peter's death in 1268, Thomas continued his claim although Philip of Savoy, archbishop of Lyon, the youngest surviving brother of his father and also sonless, succeeded in the county and was recognized.

Thomas' eldest son and heir Thomas III felt an injustice in being surpassed by younger brothers of his father, and claimed unsuccessfully Savoy from his uncles.

Thomas III married in 1274 to Guia of Burgundy, the stepdaughter of his uncle Philip I of Savoy and they had five children:

1. Philip, first of the line
   Branch
   A branch or tree branch is a woody structural member connected to but not part of the central trunk of a tree...
   
    of Savoy-Achaea, lasting from 1285 to 1418
2. Peter
3. Thomas
4. Amadeus
5. William

Philip and Thomas were in dispute much of their reigns 1268–82. Thomas' marriage was a rather unsuccessful attempt to patch up things and get Philip to recognize hims as the successor in Savoy, which would have belonged to Thomas, him being the eldest son of Thomas II and thus the founder of the genealogically senior line of the House of Savoy.

However, ultimately count Philip made Amadeus V of Savoy (1249–1323), the next younger brother of Thomas III as his heir in Savoy. Amadeus founded the line of Counts of Savoy which continues to modern days and until 1418, the extinction of Thomas III's line, was genealogically a cadet branch

Cadet branch

Cadet branch is a term in genealogy to describe the lineage of the descendants of the younger sons of a monarch or patriarch. In the ruling dynasties and noble families of much of Europe and Asia, the family's major assets – titles, realms, fiefs, property and income – have...

 of this House.

Thomas III predeceased his uncle Philip.

Ancestry