Bona Sforza was undoubtedly an intelligent person with broad horizons and even broader ambitions. She did not, however, see to the material security of her daughters Catherine and Anne. The former, however - with the support of her brother - became Queen of Sweden, whose tombstone is in Uppsala Cathedral.

Catherine Jagiellon was the youngest daughter of Bona and Sigismund I the Old. She was born on 1 November 1526 in Kraków and spent many years of her life in the castle there. Being at Wawel Castle undoubtedly developed in her a sensitivity to Renaissance art, so eagerly promoted later in Sweden. However, we know little about the princess' education. It was probably not a thorough one; she seems to have studied mainly languages, i.e. Latin and Italian. She spent a lot of time in the company of her older sisters, Sophia (b. 1522, later wife of Henry II, Duke of Brunswick) and Anne (b. 1523, later Queen of Poland and wife of Stefan Batory), with whom she maintained good relations also in adulthood.

The lives of Katarzyna, Anna and Zofia became complicated after the death of Sigismund the Old (d. 1548), when Bona moved with them to Mazovia. Shortly afterwards - in early 1556. - Sophie married and left the family nest, leaving her sisters in the country. In the same year, the queen mother left Poland, moving to Bari. She then left both daughters in charge of their brother, later King Sigismund II Augustus, but did not provide them with financial security. Bona also failed to ensure that Catherine and Anne were given in marriage. Although candidates appeared, they did not gain the approval of either the princesses' mother or brother. Albrecht Hohenzollern, for example, tried for the hand of the youngest princess, but Sigismund Augustus feared that the Prussian prince might come to an understanding with the royal opposition and threaten his reign. His proposal to marry Archduke Ferdinand Habsburg also failed.

In 1560, Moscow representatives appeared at the court of Sigismund Augustus. The purpose of their visit was to negotiate the terms of the marriage of one of the princesses to Tsar Ivan IV the Terrible, and thus also to arrange diplomatic relations between the two countries and to gain access to part of Inflants. The Tsar was keen to 'bind himself by blood' to the Jagiellonians to increase his prestige in Europe; in return, he guaranteed a perpetual peace with Lithuania. The timing of the Moscow envoys' mission was no coincidence - the First Northern War was underway, and thus the struggle for dominance over the Baltic Sea. Already at that time, Ivan IV the Terrible realised that although he was successful in Inflants, he would not conquer it on his own in its entirety. At the same time, Frederick II was on the Danish throne and Eric XIV on the Swedish throne, both of whom also showed interest in Inflants. At this stage of the war, therefore, the only way to gain access to part of the disputed territory was to marry a Polish princess. When Muscovite envoys arrived in Vilnius to negotiate the terms of the alliance, they also identified what they considered a suitable candidate for the tsar's wife - Catherine. Sigismund Augustus did not support the tsar's proposal, but delayed his final answer, explaining, among other things, religious differences. The prolonged talks were perceived by Ivan IV's envoys as a refusal.

The following year, another envoy appeared at the Polish court, this time from John Vasa, brother of the Swedish monarch Eric XIV. The growing conflict between Eric and Jan prompted the latter to seek an ally on the other side of the Baltic; the alliance was intended to strengthen Jan's position and enable him to oppose his brother. Sigismund Augustus, on the other hand, hoped to stop Swedish attempts to seize Inflants thanks to his brother-in-law from the Vasa dynasty. He therefore agreed to his sister's marriage. In the summer of 1562, Jan Vasa arrived in Gdańsk and soon travelled to Vilnius. In view of the approaching winter and the need to return to Jan's home town of Åbo (now Turku), it was decided to bring forward the wedding ceremony, which was organised on 4 October. Shortly afterwards, Catherine, accompanied by her husband, as well as dozens of people and rich equipment, set off for Finland.

The growing conflict with Eric XIV, led to the imprisonment of John and Catherine in Gripsholm Castle. After assuming the throne, Catherine Jagiellon did not, like her mother, become actively involved in her husband's political activities. Throughout her reign, she tried to maintain good relations between Poland and Sweden, especially during the period of friction during the reign of Stefan Batory and her sister Anna. She was undoubtedly influential in developing her husband's interest in the Renaissance, especially in architecture.

The queen died on 16 September 1583 in Stockholm and was buried in Uppsala Cathedral in the so-called Jagiellonian Chapel; this is located at the eastern end of the cathedral and is one of the oldest parts of the church. The court sculptor, Willem Boy, made the tombstone from marble, limestone and alabaster. On the floor, in the centre, is the inscription in Latin "Katharina Regina Svecii" along with three crowns, the symbol of Sweden, and the coat of arms of the Republic. A representation of Krakow was placed above the tombstone. Next to the Queen was buried her husband, John III Vasa, whose tombstone was made by Wilhelm van den Blocke, commissioned by the royal couple's son, King Sigismund III Vasa of Poland.