Who is Hamas chief negotiator Khalil Al-Hayya?

(Reuters) -Khalil Al-Hayya, the senior Hamas official who survived an Israeli raid on Qatar last month, was heading back to indirect talks with Israeli counterparts on Monday over President Donald Trump's plan to end the Gaza War. Hayya, who lost a son in the current Gaza war and two sons in previous conflicts, has been based with other Hamas leaders in Doha. He has become increasingly influential in the militant group as other top Hamas officials have been killed in Israeli strikes, among them Ismail Haniyeh on a visit to Iran and Yahya Sinwar in the Gaza Strip.