He was born on 1 August in Copenhagen, the son of the Royal confessor (Danish: kongelig confessionarius[1]) Iver Brinck (1665-1728) and Sophie Seidelin (1693-1741).

Brinck-Seidelin's maternal uncle, Hans Hansen Seidelin, had no male heirs.

He therefore endowed the estates Hagestedgård and Holbæk Ladegård to Hans Diedrik Brinck-Seidelin with the intention that they be turned into a stamhus (entailed estate or family trust) for future generations of the Seidelin family.

Brinck-Seidelin purchased Eriksholm and established Stamhuset Hagested from his now three estates in 1752.

Hagestedgård was, however, with royal approbation, sold to Carl Adolph von Castenschiold in 1769.