"The Cousin" was a high ranking member of the Three Families.
When Ellis Hartley Monroe was kidnapped by the Families in 2011, she was bound and gagged in a car where she was contacted by the Cousin, who informed her that since she had lost favour to Oswald Danes and her strategy was running the risk of showing the group's intentions too soon, she was no longer needed. The car was then compacted. (TV: Escape to LA)
To protect the Blessing from further interference, the Cousin, who was in Buenos Aires and another high-ranking member of the Families in Shanghai planned to bury it by destroying the surrounding structures in both cities. He shot Esther Drummond to provoke Rex Matheson and Jack Harkness not to negate the miracle but they did anyway. Just after the miracle had ended, he was thrown over the edge by Rex, falling into the blessing and killing him. (TV: The Blood Line)