[1] The fourth of six children,[4] she enjoyed the outdoors as a child, and when asked about her future she claimed "a vet was my reply ever and always.

[4] The Oxford Dictionary of National Biography states that there is reason to believe that Byrne and Cust "lived as man and wife and that she had two daughters, born in Scotland, who were later adopted".

[1] In 1904 she was briefly engaged to Bertram Widdington, the son of her former guardian, but following objections from his family regarding her career, the wedding did not go ahead.

[10]) Upon the outbreak of the First World War in 1914, Cust left Ireland to volunteer at the front and appears to have aided in the treatment and care of horses,[6][4] working with the YMCA from a base near Abbeville.

[11] The Royal College of Veterinary Surgeons in London did not recognise Cust's right to practice in her own right in Britain until 1922,[12] following the enactment of the Sex Disqualification (Removal) Act 1919.

[6] Upon her death she left the RCVS a sum of money to found the Aleen Cust Research Scholarship.