Zaid al-Hilli told ITV News that his family was "very encouraged" by the arrest made in the investigation into the death of his brother and his family.
"We are very encouraged by the recent developments. Hopefully we will get to the truth," he said.
But he added: "I don't want to raise my hopes."
More top news
County lines crime is to be targeted in a new scheme designed to steer young people and children away from exploitative gangs.
Freezing temperatures, a biting wind and risk of snow into next week
Austerity and Brexit are dividing Britons and causing a "schism" in society, the Archbishop of Canterbury has warned.