ABC News' Dan Harris, Felicia Patinkin and Jennifer Pereira report:
While much of the media maelstrom about the Tom Cruise-Katie Holmes split has centered around their 6-year-old daughter Suri, the actor has two older children who've stayed largely out of the limelight.
Those children, Connor, 17, and Bella, 19, were adopted by Cruise and Nicole Kidman after he and the actress were married in 1990.
They obtained joint custody of the children when they divorced in 2001, although Connor and Bella opted to stay in Los Angeles with their father when their mother moved to Australia.
Cruise, one of Hollywood's most successful stars and an outspoken member of the Church of Scientology, raised Connor and Bella in the faith.
"Scientology plays a huge role in Connor and Bella's life ever since they were children," Carlos Greer, of People magazine, said in an interview that aired today on "Good Morning America." "They were home-schooled and their homeschooling was really Scientology-based."
Sources close to Holmes said her husband's devotion to Scientology was one of the reasons she filed for divorce.
Connor Cruise and his father are particularly close. Father and son were on a movie set in Iceland when news broke that the actress had sought a divorce.
Holmes, 33, filed on June 28, and has petitioned for sole custody of her daughter. She and Cruise, who turned 50 on Tuesday, had been married since 2006.
"Connor is actually following in his dad's footsteps," Greer said. "You know he's acting, he's like his Dad in the sense that he seems to be craving the limelight right now. And even as his Dad goes through this with Katie Holmes and with the divorce, Connor is right by his side."
Connor's parents don't allow him to give interviews, but he is very active on Twitter. He posted a shirtless picture that made waves, and started a deejay career under the name C-Squared - scoring gigs for up to $10,000.
His budding acting career has included appearing as a young Will Smith in the film "Seven Pounds." He'll also appear in the upcoming re-make of the movie "Red Dawn."
Bella Cruise is more low-key. She has done some apprentice work for Holmes' fashion label, but an article published in the Hollywood Reporter this week claimed she was "abruptly fired about two months ago," perhaps as part of Katie's exit plan from the marriage.
Bella Cruise has a boyfriend - musician Eddie Frencher - and she has reportedly said they are both proud Scientologists.
There have been questions about just how close Cruise's older children are to their mother.
"My kids don't call me 'Mommy,'" Kidman told "GMTV," a British morning show, in a 2007 interview. "They don't even call me 'Mom.' They call me 'Nicole,' which I hate and tell them off for it."
Marty Rathbun, a former top lieutenant to David Miscavige, the head of the Church of Scientology, told ABC News that he witnessed Scientology official Tommy Davis use the religion to manipulate Kidman's relationship with her children.
"The idea was to push them toward Scientology, towards Tom and his influence, toward becoming Scientologists, and away from Nicole, who was clearly sour on the subject," said Rathbun.
When asked if the church deliberately turned the children against their mother, Rathbun replied, "Absolutely."
Connor and Bella's relationship with Holmes was reportedly very warm - at least, up until the divorce filing.
"Connor and Bella were apparently very close to Katie. She's talked about them in interviews. Tom has talked about their relationships in interviews. And there were even reports that they were so close that they even called her 'Mom' sometimes. So they had a really good relationship," Greer said.
Observers say may also have filed for divorce to prevent what happened to Kidman and her children from happening to her and Suri.
Rathbun still considers himself to be a Scientologist, but he left the church in 2004. He has been called a heretic and liar by Scientology officials who also call him one of several "excommunicated self-promoters (including one [Rathbun] who is currently promoting a book) who appear to be shamelessly exploiting a private and personal family matter for their own personal financial gain and/or self interests."
In a statement to ABC News, Davis denies ever talking with Cruise's children about Kidman.
"Marty Rathbun never witnessed conversations between me and Isabella and Connor Cruise about their mother because no such conversations ever occurred. I have never spoken with Isabella or Connor about their mother and never would as it is none of my business."
An attorney with Greenberg Glusker Fields Claman & Machtinger LLP, the Los Angeles law firm representing Tom and his two older children, also issued a statement to ABC News denying Rathbun's claims.
"Mr. Rathbun is attempting to use Bella and Connor as pawns in his vendetta against the Church of Scientology. What he says is completely false and is nothing more than an attempt to drive a wedge between Bella and Connor and their mother, and the religion her children practice. This is a violation of their privacy. Connor is a minor. Leave them out of this."