He had three sons and one daughter, who became connected by marriage with some of the principal and most ancient families of Guernsey; namely, William, married to Judith, daughter of James De Beauvoir, Esq.;[4] John, married to Elizabeth De Lisle, daughter of the then lieutenant-bailiff of the island; Henry, married to Susan Saumarez, sister of the late Admiral Lord de Saumarez; and Mary, wife of John Le Marchant, Esq[5] John Brock, Esq., born January 24, 1729, second son of the above-named William, had by his wife, Elizabeth De Lisle, a very numerous family of ten sons and four daughters, of whom eight sons and two daughters reached maturity.

He died in June, 1777, at Dinan, in Brittany, whither he had gone for the benefit of the waters, at the early age of forty-eight years.[6] In his youth he was a midshipman in the navy, and in that capacity had made a voyage to India, which was then considered a great undertaking.

As he was possessed of much activity of mind and considerable talent, his death was an irreparable loss to his children, who were of an age to require all the care and counsels of a father; the eldest, John, having only completed his seventeenth year.

They were left in independent, if not in affluent, circumstances; but the fond indulgence of a widowed mother, who could deny them no enjoyment, tended, notwithstanding their long minority, to diminish their patrimony.
Isaac Brock, the eighth son, was born in the parish of St.Peter-Port, Guernsey, on the 6th of October, 1769, the year which gave birth to Napoleon and Wellington.

In his boyhood he was, like his brothers, unusually tall, robust, and precocious, and, with an appearance much beyond his age, remarkable chiefly for extreme gentleness.