Perhaps a closer Sino-Pakistani military relationship? When at some point India makes a claim of sovereignty over the whole of Kashmir, the Pakistanis invite the Chinese to provide additional military support, effectively beginning a Chinese occupation of Kashmir, with the consent of Islamabad. Also, Pakistan's closer feelings of friendship and protection from China means that they never develop their own nuclear weapons programme.
Then, the Cold War ends. India and China are both capitalist now, and quickly begin improving their relations. Pakistan is left in the cold and suffers from a wide-scale (*?)Taliban insurrection, (TTL's Pakistan is much less martial in character). China, still having a large military presence in Kashmir, choses to annex the region outright, rather than let Taliban militants gain a breeding ground so close to the sensitive Uighuristan region.