In 1701 [his grandfather] Alexander Montgomerie 8th Earl Eglinton (age 63) died. His son [his father] Alexander Montgomerie 9th Earl Eglinton (age 41) succeeded 9th Earl Eglinton. [his mother] Susanna Kennedy Countess Winton (age 11) by marriage Countess Winton.

On 18 Feb 1729 [his father] Alexander Montgomerie 9th Earl Eglinton (age 69) died. His son [his brother] Alexander Montgomerie 10th Earl Eglinton (age 6) succeeded 10th Earl Eglinton.

On 08 Jul 1767 William Twysden 6th Baronet (age 37) died. His son [his future brother-in-law] William Jervis Twysden 7th Baronet (age 7) succeeded 7th Baronet Twysden of Roydon in Kent.

On 25 Oct 1769 [his brother] Alexander Montgomerie 10th Earl Eglinton (age 46) was shot and killed by an excise officer or Gaudger (Scots) named Mungo Campbell on 24 Oct 1769 following a dispute about the latter's right to bear arms on the Earl's grounds. The Earl died from his abdominal wounds late that evening. Campbell was convicted of murder but died by his own hand before the sentence could be carried out. His brother Archibald Montgomerie 11th Earl Eglinton (age 43) succeeded 11th Earl Eglinton.

In 1778 [his wife] Jean aka Jane Lindsay Countess Eglinton died.

On 18 Mar 1780 [his mother] Susanna Kennedy Countess Winton (age 90) died at Auchans Castle, Auchans.

After 1795 [his former wife] Frances Twysden (age 32) died.

On 30 Oct 1796 Archibald Montgomerie 11th Earl Eglinton (age 70) died at Eglinton Castle, Kilwinning. His third cousin Hugh Montgomerie 12th Earl Eglinton (age 56) succeeded 12th Earl Eglinton.