A Hamburg branch descended from the banker and renowned theatre director Abel Seyler became by marriage a part of the Berenberg banking dynasty, co-owners of Berenberg Bank and part of Hamburg's ruling class of Hanseaten.
[1][2][3] He was married to Rosina Stöcklin (1612–1681), daughter of the Basel council member Matthys Stöcklin (1577-1649), and they were the parents of Margaretha Seyler (1639–1695), who married Professor of Ethics, Rhetoric and Law Simon Battier (1629–1681), and of the noted Calvinist theologian Friedrich Seyler (1642–1708).
Friedrich Seyler was pastor at St. Peter's Church in Basel and wrote a history of Anabaptism and a refutation of Anabaptist "errors.
Anna Katharina Burckhardt was a descendant of the famous publisher and humanist Johann Froben and many of her ancestors had been councillors and burgomasters of Basel.
The company went spectacularly bankrupt in what was termed a "malicious bankruptcy" with 3 million Mark Banco, an enormous sum, in debts, but Seyler and Tillemann were able to retain some of their fortunes.
[10] Subsequently, Seyler devoted himself completely to the theatre, first as the main financial backer of the Hamburgische Entreprise (the Hamburg National Theatre), collaborating closely with its dramaturge Gotthold Ephraim Lessing, and subsequently as the founder and director of the Seyler theatrical company, becoming "the leading patron of German theatre" in his lifetime and employing some of Germany's foremost actors, playwrights and composers.
[11] He inter alia commissioned the play Sturm und Drang by Klinger, that gave its name to the era.
In 1772, Abel Seyler married his long-time mistress Friederike Sophie Seyler (1737/1738–1789), who was alongside Friederike Caroline Neuber Germany's leading actress of the 18th century, and who wrote the Singspiel Hüon und Amande that was a major inspiration for the libretto of the opera The Magic Flute.