Who are Rab’s family and where does Johnny meet them?

Rab is an orphan but he has an extended family out in Lexington. Johnny would have met them there. Every Friday, Johnny goes with Rab to visit Rab’s family outside of Boston. On one such visit, they go to a country barn dance. Rab and Johnny both have fun dancing with the girls. Johnny notices that the girls don’t seem disgusted by his hand.