Kuboni was born in Johannesburg. Like his father, Gabriel Kuboni, he was a sculptor. According to Julius, his father had the most influence on his work as a sculptor. He attended the Lamontville High School until 1982 and was taught art by George Msimang.
In 1994 and 1995 he attended woodcarving workshops held at the Technikon Natal and received a Certificates in Wood Carving. He taught art in 1995 at Bhekuzulu High School, Nongoma.
He participated in a number of exhibitions held at the Durban Art Gallery and at the African Art Centre. In 1995 his work was included in the exhibition entitled Siyawela - Love, Loss and Liberation, which was held in Gas Hall, Chamberlain Square, Museum and Art Gallery, Birmingham, UK.
He travelled over to be present at the exhibition. In 1998 he won second prize in the outdoor sculpture competition/exhibition held at the Botanic Gardens, Durban. His work is represented in public and private collections in SA and abroad.