Guggi was born in Dublin in 1959. He grew up with and remains best friends with U2's Bono. In 1984 he left the Virgin Prunes to pursue his passion for art. Since then he has exhibited his minimalistic paintings, representations of bowls and vessels, in various galleries, among which the Tony Shafrazi Gallery in New York, the Osborne Samuel Gallery in London and the Solomon Gallery in Dublin.
He is the older brother of Peter Rowen, a photographer who as a child appeared on many of U2's release covers, and Johnny Rowen, a musician. Another brother, Trevor (Strongman), played bass in The Virgin Prunes.
He lives in Dublin with his wife Sibylle and their five sons.