James Boswell's uncle John was a member of a sect known as the Glasites.
Diederik Jacob van Tuyll van SerooskerkenBorn Nov 02, 1706
Died Sep 01, 1776
Son of Reinout Gerard van Tuyll van Serooskerken (1677-1729) and Isabella Agneta Hoeufft van Fontaine Pereuse (1683-1725). Married (1739) to Helena Jacoba de Vicq. Father of Isabella van Tuyll (Belle de Zuylen).
According to Boswell "Heer van Zuylen is one of the most ancient nobleman in the Seven Provinces, and he is very wealthy too, for he married an Amsterdam lady, a merchant's daughter, with a great deal of money". (Boswell in Holland 1763-64, p. 135)
Life with Boswell:
Boswell met van Tuyll at some time during autumn or winter of 1763-64. They seem to have taken a mutual liking to each other, and Boswell revealed at least some of his secrets and corresponded on a fairly intimate level with van Tuyll, the father of his sometime love interest Belle de Zuylen. The first direct mention of van Tuyll in Boswell in Holland 1763-64 is in one of his Dutch themes, dated February 7, 1764. Boswell described him as "very polite; indeed, he received me even in the style of a friend".