The Sekundogeniturpalast is - or rather was - a palace in Salzburg. The so-called "Sekundogenitur" is the family of the second-born son in a dynasty; the first-born son′s family is the Primogenitur. In the 17th century, Prince Archbishop Paris Lodron built two palaces for his closer family to tie it closely to Salzburg. Both Primogeniturpalast and Sekundogeniturpalast were integrated into a Baroque ensemble that was formally tied in by the Baroque star architect Johann Bernhard Fischer von Erlach.
Appropriately, the Sekundogeniturpalast can be found on Paris Lodron Staße, more or less opposite the Loretokloster nunnery. Just like most of the surrounding buildings, the Sekundogeniturpalast burnt down in the great fire of 1818. It was not re-built, but parts of the fašade and a gate with the Lodron coat of arms were preserved and integrated into the current, 19th century building on this site. A fate not too dissimilar from the one of the Primogeniturpalast.
The division of families into two noble branches was not very common and should be seen in the historic context: The Lodron family was a dynasty of ambitious noblemen from the Trento in today′s Italy. Paris Lodron′s uncle managed to establish the family in Salzburg; after Paris Lodron became Prince Archbishop, he "imported" many family members and placed them into positions of power to ensure a lasting influence of his line in Salzburg. He did no rather successfully: Since the 17th century, the Lodrons were among the most powerful families in the city; their burial site was in the Loretokirche church.
Sekundogeniturpalast at SalzburgWiki (German)