She is the little sister. She was a writer for the NBC show “Parks and Recreation,” is a regular on the Fox comedy “Brooklyn Nine-Nine” and is the executive producer of a series based on the Twitter sensation Joanne the Scammer.

He is the big brother. As a founder, also, of The Huffington Post, he has shown acumen for building businesses around viral content and memes. (Earlier this week, and many weeks after this brother-sister date, rumors spread around the web that BuzzFeed plans to raise money through an initial public offering. Carole Robinson, a spokeswoman for BuzzFeed, declined to comment.)

Mr. Peretti, his wife, Andrea Harner, and their twin sons moved to Los Angeles in 2015. The siblings are making the most of the proximity. They share meals regularly, with their spouses and otherwise. They screen movies. They even tried a group game of “Dungeons & Dragons,” an activity usually exclusive to Ms. Peretti and his sons. And they spent Thanksgiving together — Mr. Peretti prepared the meal using only foods available during the Pilgrims’ time — though not Christmas or Hanukkah. “We did a sort of gift exchange,” Ms. Peretti said. “Well, I gave gifts to Jonah. Jonah never gives gifts to me. Go ahead, defend yourself.”

He began to say, “There are some things that are private that I’d rather not talk about …” when his sister piped back in.

“Actually he did give me a 23andMe genetic test,” she continued. “I’m like, are you trying to say we’re not related?”

Their shared sense of humor should put that idea to rest. Although Ms. Peretti is hipper and droller, and Mr. Peretti is geekier, their wit binds them.