On Tuesday, the 23-year-old man was back home with his father, about a week after he walked into the United States Consulate in Guadalajara, Mexico, identified himself and asked to come home to the U.S.
His return 18 years after he went missing buoyed investigators who hope Nathan's return leads to a bigger reunion with his siblings and their father, Steve Slinkard.
"We all thought that after all the kids were legal that this would happen. It's just awesome that it still happened after all these years," said Hancock County Sheriff's Department Lt. Ted Munden, the last local investigator in the case.
Nathan Slinkard was 5, his brother, Andrew, was 7, and their sister, Sydney, was 3 in October 1995 when they went missing from Greenfield, a city about 20 miles east of Indianapolis. Authorities say their mother, Trena Slinkard, failed to return them despite a court order after their father filed a motion seeking full custody.
It wasn't immediately clear when the children were taken out of the United States, or under what circumstances Nathan Slinkard and the others separated.
Investigators had tried to track the family for years, Munden said. He said officers regularly pursued tips about possible sightings, but they always proved false.
Then Nathan Slinkard walked into the consulate office and provided his Social Security card and birth certificate to consulate officials, who also used scars to confirm his identity.
"It's great," Munden said.
Nathan Slinkard arrived in Indianapolis last week after a stop in Houston, the Hancock County Sheriff's Department and National Center for Missing and Exploited Children said Tuesday. He's been reunited with his father and aunt.
"He's staying with Dad right now," Munden said Tuesday. "He's a good kid, lots of ambitions."
The whereabouts of his siblings aren't known. Munden said Nathan Slinkard hadn't divulged the others' locations but said they were safe and unconfined. Munden said Andrew and Sydney apparently know they are free to return to the U.S. if they desire.
"They're just not ready to do that yet," he said.
Munden said there is still a state warrant for Trena Slinkard's arrest in the custody case but that police "would be more than happy to drop that warrant if they wanted to come back."
His only caveat is that investigators would want Trina Slinkard to have "one sit down with Steve and the three children."
The Slinkards have requested privacy and did not return phone calls and emails seeking comment.
Associated Press writer Ken Kusmer in Indianapolis contributed to this report.