[4][5] In 1539 Dormer married Katherine (née Dallam), and he and his wife resided for a time at The Key, a property which her former husband, Richard Collier (d.1533), had purchased in 1520.
[6] It was said to have been "an extensive holding on the south side of Cheapside, almost opposite Mercers' Hall, in the parish of St Pancras, Soper Lane".
Collier's children had both died by 1540 and the Mercers "had to persuade the widow and sole surviving executor, Katherine, now married to Sir Michael Dormer, to establish the school".
[12][13] Dormer married firstly, before 1505, a wife named Elizabeth Davye, by whom he had six sons, Thomas, William, Geoffrey, John, Ambrose and Walter (a cleric), and a daughter, Joan, who married firstly James Bolney (d.1536), by whom she had a daughter, Agnes; secondly Edward Borlase (d.1544); and thirdly, Anthony Stapleton, by whom she had two sons, Michael and Amyas, who died without issue.
Katherine Dallam's first husband was a London Mercer, Richard Collier (d.1533), the founder of Collyer's School in Horsham, Sussex, by whom she had a son and daughter, George and Dorothy.