Liam O'Brien

Liam O'Brien (c. 1729 – unknown) was a member of the Assassin Order operating in the British Colonies during the Seven Years' War. A childhood friend of Shay Cormac, Liam was responsible for bringing Shay into the Brotherhood. Being a few years older than him, Shay formed a brotherly bond with Liam even though he was a lot wiser and more experienced.

Reference

 * AC Initiates podcast

Trivia

 * Liam O'Brian is also the name of a real life voice actor.