I decided to replace Christina with her sister Dorothea as wife of Sigismund Augustus, IOTL both were childless, so they'll be ITTL. Bona's child after Olbracht/Albert also is possible, although considering Sigismund I's age, not very likely, but let's give them little Barbara, born in 1530. So now we have:
-Hedwig (Jadwiga), married to Ferdinand
-Isabella (Izabela) married to Dauphin
- Sigismund Augustus (Zygmunt August), married to Dorothea of Denmark
-Anna, married to Albert of Bavaria
-Catherine (Katarzyna), married to Charles Victor of Brunswick
-Albert (Olbracht/Alberto), married to Anna d'Este
-Barbara, married to John George Hohenzollern, Elector of Brandenburg, or to Albert Hohenzollern, Duke of Prussia (rather the former, Albert certainly would be interested, but as first cousin and former clergyman he'll be problematic candidate, and due to fact, that Hedwig never married Joachim II there is stronger need for Jagiellon match with Brandenburg Hohenzollerns).
Surviving brother and different wife means great changes in life of Sigismund Augustus-Bona would not be as overprotective as IOTL. Healthly first wife means, that Sigismund would not be able to remarry (Dorothea lived untill 1580, and there is no chance to get annulment, Dorothea is Emperor's niece and Sigismund Augustus is not Henry VIII, he'll not risk religious conflict to be able to get new wife, especially considering the fact, that he had male heir already)), Barbara Radziwiłł may appear in his life, but would be only his mistress, not wife. So Sigismund's conflict over Barbara with rest of his family and with nobility of both realms would be avoided. King, who has mistress is nothing unusuall, unlike non-dynastic marriage from love. Bona would dislike Dorothea, blaming her for lack of children, but there is spare son, who'll have large family with Anna d'Este, so future of Dynasty is safe. Olbracht, after spending most of his life in Italy, would face serious problems after ascending the thrones of Poland and Lithuania, being almost foreigner not very familiar with political landscape.