Thomas I was born into the gens Monoszló as the son of Macarius I, who functioned as ispán of Szolnok County between 1192 and 1193. His mother was an unidentified daughter of Peter Győr from the Szenterzsébet branch. He had two brothers, Nicholas I and Stephen I, who remained only lesser Slavonian landowners without political significance. He had five known children from his unidentified wife. His son, Gregory II served as ispán of Krassó County around 1255 and was father of three notable barons, Egyed II, Gregory III and prelate Peter II. His second son, Thomas II remained marginal among his contemporaries, but the influential 14–15th-century Csupor family descended from his line. Thomas I also had at least four daughters, three of them are unidentified, while Nabut married James from the Héder clan, a great-grandson of PalatineHéder, and was still alive in 1283.
Career
Thomas was a long-time supporter of Duke Andrew, who rebelled against the realm of his brother, King Emeric at several times. He was present, when Andrew planned a new rebellion against Emeric, but the king walked into his brother's camp unarmed and captured him without resistance near Varaždin in October 1203. Alongside Andrew, Thomas was held in captivity for months, but the Duke's supporters released them in early 1204. After Andrew's ascension to the Hungarian throne in May 1205, Thomas was promoted to a royal knight. He participated and seriously wounded in one of Andrew's military campaign against Halych in late 1200s. When Andrew II led the Fifth Crusade to the Holy Land from 1217 to 1218, a group of barons took advantage of the situation and rebelled against the king, but Thomas remained loyal to Andrew when the kingdom was in a constant state of anarchy during the king's absence. He served as ispán of Valkó County in 1221. In the next year, already a certain Kozma held that office. He fought in Coloman's campaign against the Principality of Halych which ended in defeat. From 1228 to 1229, Thomas functioned as Ban of Slavonia under Coloman, who adopted the title Duke of Slavonia earlier in 1226. For his merits, Thomas was granted lands in Bács, Csanád and Valkó Counties, as well as the lucrative fishpond in Zagreb. As sole secular nobleman, Thomas also received permission from Andrew II to trade salt with six riverboats across the Maros at three times a year. In 1231, Thomas spun off his own lands from the kindred's property. He died before 1237, when his four daughters were still maidens.
