Allan was Robert Kerr and Flora's youngest son. With Allan's improvements to the gardens and grounds of Erchless, the estate became the elegant property it remains today.

Allan added the Coach House, Carriage Path, Tennis Courts and the ornamental Gate which still stands at the north entrance to the property. As well, Allan modified the driveway that led to Erchless' front doors. Flora was very opposed to changing the existing driveway, and the story goes that Alan took advantage of his mother's extended absence from the home one season, and extensively changed the driveway. It was upon her return to Erchless that Flora found a gravel driveway that curved and exited to King Street.

Allan was a lover of horses and of riding; this love of horseflesh, when added with his enthusiasm for sailing, meant that Allan was known for having fabulous parties on the grounds of Erchless.

Flora willed the property to Allan on her death in 1918, and Allan died shortly after his mother in that same year. When Allan died he left the estate to his brothers and sisters, who in turn sold it to Emelda Beeler Chisholm, the wife of their cousin John A. Chisholm Jr.