Verelst was born in 1717, the only son of Johann Louis Verelst in Veere in the province of Zeeland. Married firstly to Sara Lydia Diodati (1723-1766), and secondly to the widowed Baroness Ilse Sophia von Kraut née von Platen (1731-1795).1
In 1750-51 he was the Dutch envoy to the Kings of Sardinia and Savoy. From 1753 he was Dutch envoy in Berlin, and at least around 1764, he acted as the Dutch ambassador to the court of Frederick II.
- 1. Ilse Sophia von Platen was the widow of Carl Friedrich von Kraut (1703-1767), who had been the Oberhofmarschall to Prince Heinrich, the younger brother of King Frederick II of Prussia. With von Kraut she had one surviving child and heir, Luise Charlotte Henriette von Kraut (1762-1819).
Boswell unknowingly insulted Verelst when, on July 8, 1764, he told Andrew Mitchell that Belle de Zuylen had "too much wit for the Dutch". Verelst was present in the room as well, but Boswell was not aware that he was the Dutch envoy. He doesn't appear to have taken too much offence, for he and Boswell dined together on July 16. On this occasion, Boswell described him as "phlegmatic, but not unjolly".