As a teenager, Kirwan's band Boilerhouse supported Fleetwood Mac at venues in London before he was invited to join the group itself in 1968.
According to Variety, no details surrounding his death are immediately available.
Fleetwood's statement concluded, "Danny's true legacy, in my mind, will forever live on in the music he wrote and played so beautifully as a part of the foundation of Fleetwood Mac, that has now endured for over fifty years". His death was reported by the band's co-founder, Mick Fleetwood, on his Facebook page.
DANNY KIRWAN MAY 13, 1950 ~ JUNE 8, 2018 A TRIBUTE FROM MICK FLEETWOOD AND FLEETWOOD MAC Today was greeted by the sad.
Back in 2015, during an interview with the New York Observer, Tim Sommer said Kirwan was one of the "great lost figures" in the history of rock music. The original United Kingdom release included seven Kirwan compositions; however, two of the songs were dropped for the album's US release on Reprise, the band's first for the label. The collection was highlighted by Kirwan's rolling composition "Station Man". Kirwan recorded five albums with the band-Then Play On, 1969's Blues Jam at Chess, 1970's Kiln House, 1971's Future Games, and 1972's Bare Trees-as a guitarist and singer at the height of their productivity.
Fleetwood Mac Guitarist Danny Kirwan Dead at 68
However, Danny's drinking continued to get worse, and he would often get into altercations with other band members, including Welch and Mick Fleetwood.
He remained active briefly, recording unsuccessful three solo albums for the British label DJM in 1975-79. During the decades that followed, he was "reportedly marred by bouts of mental health issues and homelessness".
Kirwan was inducted into the Rock and Roll Hall of Fame in 1998 as a member of Fleetwood Mac.
Kirwan is survived by his only son.