His father, Lepani Kaiuwekalu Watson, had worked for the Australian colonial administration and became premier of Milne Bay Province in 1983.
Lepani was asked by the country's first prime minister, Michael Somare, to become head of the National Planning Office, a position he stayed in for almost six years.
During this time, he, together with Mekere Morauta, Rabbie Namaliu and Anthony Siaguru, who were all involved in different ministries coordinating policy development and government programmes, were known as the "Gang of Four".
According to Lepani, this rather pejorative name came from older Papua New Guineans, who had worked with the colonial administration and resented the authority of the younger men.
[5][6] Lepani then studied for a master's degree in public administration from the Harvard Kennedy School in Cambridge, Massachusetts in the US, receiving a Fulbright scholarship.
[1][5] In July 2020, it was announced that Lepani would become a member of the board of Geopacific Resources Ltd, a company involved in gold mining on Woodlark Island in Milne Bay Province.