At the beginning of The Force Awakens, when the Stormtroopers grab Lor San Tekka and bring him to Kylo Ren, Ren says "Look how old you've become". To me this suggests they were acquainted in the past- does anyone know more than that?
Lor was apparently an ally of the New Republic and Leia's fledgling Resistance, working with them to provide intel and Luke with information about the pre-Imperial Era Jedi Order.
A legendary traveler and explorer, Lor San Tekka is a longtime ally of the New Republic and the Resistance. After the Battle of Endor, San Tekka helped Luke Skywalker recover secret Jedi lore that the Empire had tried to erase, and Leia Organa hopes the old scout can now help find her brother. Following decades of adventure, San Tekka retired to live simply on Jakku, where he follows the dictates of the once-forbidden Church of the Force. But his retirement is fated to be anything but peaceful.
AS THE EMPIRE TOPPLED, retreating Imperial officials destroyed records that would have been vital to the New Republic's attempts at galactic reconstruction. New Republic bureaucrats turned instead to firsthand accounts from well-traveled locals to fill in the gaps. A seasoned traveler and explorer of the more remote fringes of the galaxy, Lor San Tekka has proven his worth to the New Republic and the Resistance many times over. Ready to retire after decades of exploration and adventure, the spiritual San Tekka has settled with a colony of villagers in the remote Kelvin Ravine on the frontier world of Jakku.
Given that he was working with both Luke and Leia at various points, it's hardly surprising that he would have met young Ben prior to him becoming a
whiny emo tantrum baby powerful adept of the dark side of The Force.