What position did Ghulam Mohammed Sadiq hold in the Indian National Congress in relation to Kashmir in the 1960s?

He was the Chief Minister of the state from Congress

Ghulam Mohammed Sadiq, a Congress leader became the first Chief Minister of the state after the constitutional change in 1965.
Between 1953 and 1974, the Congress party wielded significant influence over the state's political landscape. During this time, a fragmented National Conference (excluding Sheikh Abdullah) held power for a period with active support from the Congress. Eventually, this faction merged with the Congress, granting the latter direct governance control in the state and instigating changes. During this period, various efforts were made to find a resolution between Sheikh Abdullah and the Indian government. In 1965, an alteration to the Jammu and Kashmir Constitution designated the state's head as the Chief Minister instead of the Prime Minister. Consequently, Ghulam Mohammed Sadiq from the Indian National Congress became the inaugural Chief Minister of the state.