He is best known for his role as Doug Carter in the Channel 4 soap opera Hollyoaks.

He originally played the role in online spin-off Hollyoaks: Freshers.

[1] Brennan lived in his native United States for the first 21 years of his life before moving to the United Kingdom after graduating from Fordham University, settling in London in September 2007.

Brennan studied at the Central School of Speech and Drama where he completed a three-year degree.

[2] Brennan later moved to Liverpool and lived with some of his Hollyoaks cast members including Alice Barlow, Bianca Hendrickse-Spendlove and Jessica Forrest.