Jaelyn Young and Muhammad Dakhlalla came from families who, according to friends and acquaintances, push for peace, law and order.
But now they're both in federal custody, facing conspiracy charges alleging a plan to travel to Syria and join ISIS.
Details are still emerging in the case, and the pair's families have been tight-lipped. Here's what we know about the Mississippi couple:
'Devastated' family stands by daughter
Jaelyn Young's father, Leonce Young, has been an officer in Vicksburg, Mississippi, for 17 years, the police department said in a statement Tuesday.
He's also served in the military for 21 years, completing 14 deployments, police said.
"The family is devastated and it is our understanding had no knowledge of or involvement in Jaelyn's plans," police said. "We understand that the Young's love their daughter and have supported her educational career and will stand by her through the legal process. At this time the Young family is going through an extremely difficult time and we would like to keep them in our thoughts and prayers."
The Young family hasn't responded to requests for comment. Ken Coghlan, an attorney representing Jaelyn Young, declined to comment.
In the spring, Jaelyn Young -- now 20 --- was registered as a sophomore studying chemistry at Mississippi State University, school spokesman Sid Salter said. She described herself as unemployed in a financial affidavit filed in court this week, noting that her mother pays her tuition bills.
In high school, she was an honors student, a cheerleader and in her school's Homecoming court, the Clarion-Ledger reported
The Vicksburg Post described her
as an "all-American girl" who participated in robotics competitions.
A law enforcement official described her as a recent convert to Islam.
In a decision denying bond Tuesday, U.S. Magistrate Judge S. Allan Alexander said there is "clear and convincing evidence" that Young had "carefully constructed a plan" to travel to Syria and serve ISIS.
"She left detailed letters to her family and 'the authorities' which all make clear her intent to join (ISIS) and never to return to the U.S.," the judge wrote.
'Like having a two-by-four right between the eyes'
Family members thought Muhammad Dakhlalla, a 22-year-old who goes by the name "Mo," was going to start graduate school in psychology at Mississippi State on Monday, said attorney Dennis Harmon, a longtime family friend.
But instead, Dakhlalla is behind bars and his parents, Harmon said, are "absolutely stunned."
"It's like having a two-by-four right between the eyes," Harmon said.
Doug Bedsaul, an instructor who trained Dakhlalla in judo and taekwondo for years, said he was surprised to hear the allegations -- and will reserve judgment until all the facts come out.
"It doesn't seem to fit with what I know of him, his personality, or his family," he said.
Bedsaul described Dakhlalla as calm, attentive and focused.
"I can't remember him ever getting upset or angry at all," Bedsaul told CNN. "I have seen him compete, and for some people, that would be a moment when they could get upset, when they were losing or being in the heat of the moment. But he always had very good control of himself."
His father, Oda Dakhlalla, originally hails from the West Bank city of Bethlehem, Harmon said. He's been an imam and taught at the local mosque, the Islamic Center of Mississippi in Starkville. He's also a private math and science tutor, Harmon said. His mother, Lisa Dakhlalla, is originally from New Jersey and has a catering business.
"When Oda teaches, he teaches Islam as peace. ... He has nothing to do with the Islam of (ISIS)," Harmon said.
Harmon represents the family but isn't involved in the federal case. A federal public defender representing Dakhlalla declined to comment.
In her decision denying bond, Alexander said Dakhlalla "participated in plans" with Young to travel to Syria, "stating his desire to serve (ISIS)" in media relations and as a fighter.
"He left a detailed letter to his parents which makes clear his choice was deliberate and voluntary," the judge wrote.
Dakhalla graduated from Mississippi State in the spring with a degree in psychology, Salter said. He described himself as unemployed in a financial affidavit, adding that his parents support him.
He and Young met when they were both studying at the school, according to Harmon, but they haven't know each other long -- maybe months or a year.
They had an informal Nikah, an Islamic wedding ceremony, Harmon said, but no civil marriage.
The family learned about Dakhlalla's arrest, Harmon said, when FBI agents knocked on their door. They let agents in to search their son's room, he said.
The family has spoken on the phone with Dakhlalla, Harmon said, and urged him to cooperate with the FBI.
"They absolutely trust the government to get the facts straight," Harmon said.