My parents came to visit in early June to get some quality time with their littlest grandson, and Jake took to them right away! I was worried that with all his issues of separation anxiety (or "mommy-itis") that he wouldn't warm up to them quickly. But he proved me wrong. It probably helped that they brought him a big, cool wagonful of giant lego blocks :-)
Every morning when they came downstairs, Jake would look at them like, "Who are you, and what are you doing in my house?" but then they'd make a silly face or noise at him and the ice would be broken. By the end of their visit, he was actually making bids for their attention as much as (if not more) than he did for mine & Ben's. It was cute.