He will compete in home arts on Saturday, which is opening day, and on Tuesday he will lead his steer.
Steffy, 10, also is competing in home arts, participating in the Saturday fashion review and baking peanut bar cookies for the bake sale.
"It's pretty fun. You get to be with all your friends," Steffy, who is announcing at the dog show Thursday, said of Ag Expo.
For the last two years, Steffy was the champion in the under $20 ready-to-wear category at the fashion review. This year she's wearing a dark pink shirt, a dress romper with the same color flowers and a matching bow. She said it's getting harder to find the right clothes for under $20.
Brian didn't have to worry about the cost of raising his steer because the Creek Bound Farm on Poffenberger Road takes care of his costs. He said he was working odd jobs on the farm when farm owner Jim Weddle asked if he wanted to raise a steer, a two-year project.
The Weddles pay for Thunder's veterinarian bills, and Brian takes care of him. At the expo, Brian, who will attend Boonsboro High School this fall, will get half of the money Thunder brings at the Aug. 8 market sale. He said he'll get a new steer after Thunder is sold.
Last year, Brian took third and fourth places for his steer, but it was his first year showing. This year he has a show under his belt, and he's ready. He spent 10 hours a day, three to four days a week at the farm taking care of Thunder.
Diane Lewis, their mother, said Brian and Steffy got into 4-H because the organization can help them gain leadership skills and confidence.