Looking for help with OUN member

[Adrian]

Please can anyone help me! I am trying to help my Ukranian grandfather with his family tree. He seems convinced that his uncle (Antin Labaj) was one of the men that worked under Stefan Bandera in the OUN, and even perhaps took over after Bandera was excecuted, but I cannot find reference to him anywhere.
If anyone has any information they could give to me I would very much appreciate it

Adrian RIchards