On 9 August 1814 he married Letitia Vesey-Fitzgerald, daughter of James Fitzgerald, with whom he had five sons and a daughter, including the Australian politician, John Foster Vesey-Fitzgerald.
In the summer of 1814 he acquired his family seat at Rathescar, Co. Louth, an estate where his uncle, John Foster had lived in the 1770s and where John Leslie Foster undertook substantial repairs and alterations.