Colm Gildernew will become Sinn Fein's new MLA for Fermanagh-South Tyrone - replacing his sister Michelle after she was elected MP for the constituency.
The 48-year-old father-of-three was chosen after a selection convention. It still has to be ratified by the party.
He said he was "proud" to have been chosen for the role.
Mr Gildernew is one of three Sinn Fein MLAs who will represent the constituency at Stormont.
He said: "I look forward to providing a new voice for the constituency alongside Jemma Dolan and Sean Lynch as well as the other Sinn Fein representatives to ensure the people of Fermanagh-South Tyrone continue to get first-class representation.
"The momentum has been building behind Sinn Fein's platform of equality, rights and Irish unity in recent years and, if my selection is approved, I will do all in my power to advance that programme.
"I am looking forward to representing all the people of Fermanagh-South Tyrone, pursuing equal rights and opportunities for all."
Mr Gildernew is well-known on the traditional music scene and is a founding member, former chairman of and current director of Aghaloo Credit Union, and a member of and keen follower of Aghaloo GAA club in Aughnacloy.
He is also a founding member of the Brantry Area Rural Development Association.
The vacancy was created after Ms Gildernew reclaimed her Westminster seat.
She defeated Tom Elliott, who had held the seat since 2015, winning with majority of 875 votes. Ms Gildernew was previously MP from 2001 to 2015.