They had their own borders before the six day war, but they could not control them as Egypt and Jordan used Gaza and the West Bank as staging grounds to attack Israel.
Had Arab Countries accepted the UN Partition Resolution in 1947, Palestinian Arabs would be celebrating 75 years of independent Palestinian statehood today with pre-1967 borders. Arab Countries initiated several wars against Israel to destroy the one tiny Jewish State and they lost each time. —- There are consequences for starting wars