Broadcaster Derryn Hinch will discover the full extent of his family tree this week, and a strange oil painting could be key to it all.

Hinch will appear on SBS program Who Do You Think You Are? on Tuesday night, and spoke to Deborah Knight on 2GB to tease the emphatic discoveries.

Among the most stunning revelations came from a generations-old oil painting of his mother, which could confirm his true lineage.

Hear more highlights from Deborah Knight below: