Silas Sugwash is Titania Tilpin's great uncle.
Silas is possibly endowed, as he studied and collected papers of information about Count Harken Badlock and Lilith, and their line of decendants. Like Paton Yewbeam, he studied the Red King's children and history of magic along their descendants. Silas died in the third book, where readers are not informed, but are noted in the fifth book when Titania says he died "last summer" which would be the third book.
Silas was married to Steffania Sugwash, who was possibly endowed and practiced magic. She wrote Collected Charms and Enchantments of Steffania Sugwash, a book with written charms, and possibly other books. Titania used Steffania's books to teach her lessons at Bloor's, and keeping a cabinet with those books, there could be other collections of spells.
Silas was one of Lilith's descendants who tried to help Count Harken get back to the Red King's City, but failed, as he had an old map of where the Count stored The Mirror of Amoret for one of his descendants to use it to bring him back.