Mackenzie’s two elder brothers died young and in 1810, when Glenbervie described him as ‘a very lively, sensible young man’,
He was expected to support the Liverpool ministry, and appears to have done so, but he showed the same liberal cast of mind as his father. He voted for Catholic relief, 2 Mar. and 24 May 1813, before and after taking leave of absence on account of illness in his family,
Mackenzie’s remaining brother died in 1813 and he too predeceased his father, 25 Aug. 1814. Lord Lauderdale related the circumstances to Lord Holland:
He was to have gone down with Maitland but was obliged to stay a day later, and went straight through in the mail coach. The day after his arrival he was seized with a violent fever which was attributed to the heat and jolting he had been exposed to. In the course of his illness however his headaches were so excruciating and the symptoms so singular that they thought it right to open his head when there appeared a bone in the shape of a lancet that had grown from the inner surface of his skull and pressed upon his brain. This Gregory says must have killed him at all events and thinks that the journey had little share even in expediting it.
Add. 51691.
