[Gil4]

After both Kerry and Alston departed Vietnam, the two stayed in contact and Kerry had invited Alston to his first wedding, to Julia Thorne in 1970, and sent Christmas cards to Alston's parents' house.

That does sound like the actions of guys who served together in some capacity. We need to be careful with this one.

[The Bandit]

They had became friends while COSDIV 11 and 13 were conducting ops. But from the chronology of Kerry's and Alston's service do not place these guys serving with each other on missions, just at the same port.