It was the year of the Lord 1234 AD. when the Sansedoni brothers decided to set up the first company "Societas Filiorum Sansedoni" that dealt with the granting of loans to third parties, traders in particular, between Siena and Paris. The first Italian private bank was born in fact and in law, as we can also read in the great work written on the "Palazzo Sansedoni" published on the occasion of the restoration of the building (Ed. Protagon - Monte dei Paschi di Siena - 2004, ITA / ENG) . Ghibelline tendency family, friend of the Swabian Emperors Corrado IV and Corradino, subsequently had a strong bond with the Church of Rome for the descent into the family of the Blessed Fra Ambrogio Sansedoni (Siena n.1220 - + 1287), Dominican of the order of preachers , who was, we recall, a pupil in Paris of Saint Alberto Magno the Great and co-disciple of Saint Thomas Aquinas and Pietro of Tarantasia (who later became Pope Innocent V). Thanks to his recognized eloquence and confirmed diplomatic skills, he managed to be an effective mediator of the thirteenth century, often also to the advantage of his city of Siena. In fact, he was sent as ambassador to Rome to intercede before the pope and restore peace between the Supreme Pontiff and the city of Siena, in Siena which was in that period for the first time Ghibelline but also ruled by Guelphs. His intervention, we recall, allowed the recovery for the most important and rich Sienese families like his, of numerous credits towards the Church of Rome, credits that had previously been frozen with the Interdict of Pope Gregory X to the Municipality of Siena . He had a great role as a peacemaker, sent by the Pope to settle the conflicts between the cities of Genoa and Venice, between Florence and Pisa, he intervened
in front of Pope Clement IV in defense of the Emperor Corradino, nephew of Frederick II, excommunicated by the Pope and condemned by King Charles of Anjou, obtaining, if not his life, the absolution for the young king. 
This dual membership of Fra Ambrogio, to enjoy great prestige at the Pontifical Court in Rome on the one hand, and on the other hand to have a sure Ghibelline imperial descent, allowed his father Bonatacca, in August 1266, "faithful to the imperial cause, who since the death of Frederick II in 1250, led with his other son Ranieri, various missions of connection between the Municipality of Siena and the heirs of the emperor, Corrado first, then Manfredi ", together with the great charisma of his son Ambrogio, of bring peace between the Municipality of Siena, the Sienese Guelph exiles, the Municipality of Orvieto and the Aldobrandeschi counts. The Municipality of Siena dedicated a palio with horses to him:

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