Christopher Guest’s television series “Family Tree,” his first major project since 2006’s “For Your Consideration,” will premiere Sunday, May 12 at 10:30pm on HBO. The new behind-the-scenes video below offers a better sense of the half-hour show than anything the network’s released so far. “We use the genealogy as an excuse to go into different worlds,” explains co-created Jim Piddock, as we get a closer look at Chris O’Dowd as Tom Chadwick, a young man who decides to track down members of his extended family after a bad breakup, accompanied by his sister Bea (Nina Conti, “Her Master’s Voice”) and his friend Pete (Tom Bennett). No sight yet of Amy Seimetz, who’s been cast as Tom’s potential love interest, but there are plenty of Guest regulars to be had. The eight-episode season was directed by Guest and, like his films, was shot mockumentary-style and improvised by the cast.