The grandchildren’s birthday parties were always lavish.

At their $6 million Annapolis mansion, Don and Sandra Pyle could never do too much for her sons’ kids, transforming the sprawling eight-acre estate into a children’s carnival with water slides, moon bounces and pony rides. Don, especially, reveled in the games of hide-and-seek and make-believe tussles.

“It was like he was raising the children he never had,” said Jon Bierman, a longtime friend of the wealthy technology executive. “He put everything into them.”

The four Boone kids — Lexi, 8, and Katie, 7, along with their first cousins Charlotte, 8, and Wes, 6 — went to a sleepover at their grandparents’ home on Sunday because Monday was a holiday, a family spokeswoman said. Don, 56, known as “Pop-Pop” to the grandkids, and Sandy, 63, who went by “Dee-Dee,” took them to Target to buy costumes for a visit to Medieval Times at the Arundel Mills mall. Together, they watched knights joust and ate dinner in a banquet setting before heading back to their own castle, as the Pyles’ 16,000-square-foot home was known to neighbors.

They almost certainly never left.

Early Monday morning, an inferno consumed the mansion, bringing down its seven-ton steel beams and reducing to ash a structure the size of seven average single-family houses.

All six family members are feared dead. So far, five bodies have been found — two Wednesday, two more on Thursday and one on Friday.

Cadaver dogs continue to hunt for the other remains as investigators search for any signs of foul play. On Thursday, they also brought in a dog that specializes in sniffing out gasoline and other accelerants that may spark fires.

Left behind are Clint and Randy Boone, who each lost two children as well as their mother and stepfather in a single night.

Clint, 37, and his ex-wife, Eve Morrison, 39, are parents to Charlotte and Wes.

Randy, 38, and Stacey, 34 — parents to Lexi and Katie — also have a newborn son, who was at home with them the night of the fire.

“I never knew that I could hurt this badly. It’s unreal,” Stacey wrote in a Facebook post Tuesday. “All one big nightmare that I can’t wake up from.”

In biographies released by the family Friday, Lexi, 8, was described as an eager big sister to her newborn brother and devoted to her dog, Sophie. She played field hockey, lacrosse and ice skated. “Lexi wanted to be a vet or on television when she grew up,” her family said. “She was going to be famous.”

Her younger sister, Katie, was also excited about the arrival of a baby brother. Katie played soccer and enjoyed gymnastics, ice skating and singing Taylor Swift songs. “For only having just turned 7,” her family said, “she was loving and thoughtful beyond her years.”

Charlotte, 8, loved horses, basketball, swimming and making videos with her guinea pig, Oreo. “She wanted to be known as a gamer with an epic love of Minecraft,” her family said. “Charlotte’s future dreams were to run an animal rescue.”

Her brother Wes, 6, “looked up to his sister immensely,” his family said. Like Charlotte, he also enjoyed Minecraft and swimming, and had a particular fondness for Legos, Doctor Who and the game “Plants vs. Zombies.” “In his future,” the family added, “Wes wanted to build robots.”

The Boones hinted at their desolation in a joint statement released Thursday, thanking firefighters, expressing gratitude for the outpouring of community support and calling the love for their family “boundless.”

“Life is fragile,” they said. “Make time today to embrace your loved ones.”

A raging fire

The four-alarm blaze was one of the most devastating in Maryland in years, according to Bruce Bouch, the senior deputy state fire marshal whose agency has been helping Anne Arundel County with its investigation.

Bouch said a home alarm alerted 911 that smoke was detected on the first and second floors of the mansion early Monday, but because of the home’s vast open areas, the fire probably spread rapidly and “overcame the space.”

“By the time the fire service was on the scene, they already had a raging, out-of-control fire they had to fight,” Bouch said.

County fire officials said there were no sprinklers in the Pyle mansion, which was built in 2005 — four years before Anne Arundel began to require them in new residential homes.

Fire sprinklers will become mandatory in all new residential buildings in Maryland starting in June. Bouch said that if sprinklers had been installed in the Pyle mansion, “there probably wouldn’t be a story today.”

Investigators are using specialty software that provides “forensic mapping,” which allows them to reconstruct a building’s layout in such detail that they could determine where drapes might have hung or a couch might have been placed, according to Special Agent Dave Cheplak, a spokesman for the Baltimore office of the Bureau of Alcohol, Tobacco, Firearms and Explosives.

He and Capt. Russell Davies Jr., a spokesman for the county’s fire department, said they had not determined the cause of the fire.

“Until we make a determination one way or another, it’s going to stay a criminal investigation,” Davies said.

Cheplak echoed the need to comb carefully through the evidence, a process that could take weeks. “Anytime you have a family of six people killed in a home, it’s certainly not commonplace,” he said. “Nobody is taking it as routine.”

He would not comment on whether the accelerant dog found anything suspicious, but he did say that cadaver dogs have been instrumental in helping crews pinpoint where to dig for bodies.

Amassing a fortune

Before it was reduced to rubble, the mansion symbolized the Pyles’ soaring success and served as the center of their family’s universe.

The couple met in 1981 at Rixon, said Nick Whelan, who had an engineering job at the Silver Spring, Md., tech company.

Don, a salesman, had recently graduated from the University of Delaware, where he played lacrosse. Sandy, a mother of two young boys, worked in marketing.

Back then, their generous philanthropy, frequent vacations, yacht club social swirl and Great Gatsby-like galas were years away.

“He was like all the rest of us working stiffs,” Whelan said. “They would go out for beers together.”

Don and Sandy shared sharp wits and the same passions. The couple frequented Orioles games and the Preakness Stakes and joined friends for happy hours at Baltimore bars. In the summer, they boated; in the winter, they took Sandy’s sons on ski trips to Pennsylvania.

“They were always very well-matched together,” he said. “They got on amazingly well.”

The two married in 1983 as Don’s career took off.

“I was able to get in on the ground floor in some of the companies that were based in Silicon Valley,” he told The Washington Post in an October interview, after becoming chief operating officer of ScienceLogic, a Northern Virginia computer networking company. And he made a fortune in the process.

During his rise in the tech world, Sandy focused her attention on her sons, who attended Mount Hebron High School in Ellicott City, Md. A friend of the brothers said their father, Kenny Boone, played an active role in their childhoods.

Randy, the older of the two boys, eventually followed in Don’s professional footsteps, holding jobs at a pair of companies his stepfather helped run: Netcordia and Infoblox, according to his LinkedIn profile. He now works as a sales development representative.

Sandy, meanwhile, became an entrepreneur, opening a tanning salon in Columbia, Md.

Jill Willingham was 15 when she started working for Sandy at Hot Off the Beach. Sandy would sign her employees up for training and seminars, encouraging their business aspirations. She also took the entire staff to conventions, including one in Ocean City.

Willingham, now 36, said she and her husband once attended a July 4 party at the mansion, which was designed to look like an English-style castle complete with a suit of armor inside.

“It was beyond anything you could imagine,” she said. “They had a lot of castle things, like a drawbridge. And there was an infinity pool. Inside, she had a current pool so she could exercise. She also had a tanning room in a tower of the house.”

Sandy, who sold the tanning salon years ago, was known for her eclectic taste and extravagant parties.

From 2008 to 2010, she and Don threw wine-tasting fundraisers for the Cal Ripken Sr. Foundation, a spokesman said. Two years ago, when the Delaware football team played Navy in Annapolis, the Pyles hosted an event for alumni and school leaders
of Don’s alma mater, said his former lacrosse coach, Bob Shillinglaw.

When Sandy’s Howard High School class needed a place to hold its 40th reunion in 2010, she offered their home.

“It was awesome in the true sense of the word,” said Sue Goodwin, a former classmate. “Their graciousness and generosity was beyond belief.”

She also had a deep love for the rescue dogs she took in, feeding them leftover prime rib or — when the family ordered pizza — their own cheeseburgers.

Still, friends said, nothing compared with the adoration they had for their grandchildren.

They turned their expansive basement into a playroom for sleepovers and took the children on trips to Disney World and Great Wolf Lodge, an indoor water park.

They helped pay for the children to attend the private Severn School, where tuition for elementary students runs nearly $18,000 a year. The family was such a fixture on campus that one parking space is marked “Reserved for Pyle family.”

Joe Heim, Steven Overly, Julie Tate and Julie Zauzmer contributed to this report.