Were Laurens, Lafayette and Mulligan really his friends?

In the musical: the four meet in a tavern in 1776 and plan revolution together.

The real friendships:
John Laurens, son of the South Carolina politician Henry Laurens, joined Washington's staff in 1777, the same year as Hamilton. Their surviving letters are unusually warm; some historians read them as romantic, others as the effusive style of the age.
Lafayette met Hamilton at Washington's headquarters in 1777; they wrote to each other for the rest of Hamilton's life.
Hercules Mulligan was a New York tailor with whom the young Hamilton lodged on arrival. During the British occupation he gathered intelligence for the patriots while serving British officers.

A note on faces: portraits survive of Laurens and Lafayette, both painted by Charles Willson Peale during the war. No authenticated portrait of Hercules Mulligan is known. Only his signature and a photograph of his grave are available in the public domain. A tailor, however successful, was not the kind of man who sat for portraits, and his intelligence work stayed secret during the war. Images labeled "Hercules Mulligan" online are usually misattributed portraits, modern illustrations or photos of actors.

Fact-check verdict: the friendships are real; the tavern meeting is dramatic license. And one of the loudest voices on stage left history without a face.