"I had tried finding them on social media, mostly Bobby, because I felt if either of them were to have a social media presence, it would be him," Mosteller said.
Mosteller posted a picture on GoFundMe of Myong and his Bobby from Christmas Day in 1988.
The day after this Christmas, Mosteller's family got devastating news.
Through modern DNA technology, authorities discovered remains that were found in 1998 in Mebane belonged to Bobby.
Other remains found in South Carolina, also unidentified for nearly two decades, were linked to Myong.
"Science has caught up to the evidence that we have in our possession and it was able to tell us that the child's mother was also murdered," said Orange County Sheriff Charles Blackwood.
Mosteller's uncle, who is in prison on unrelated charges, is suspected of murdering them.
"It has made me sick," Mosteller said. "I've had days where I was physically ill from this."
Mosteller said her uncle had told the family Myong and Bobby went to South Korea to be with her family.
A family member of Bobby Whitt shared these old pictures of Bobby and his mom, Myong Hwa Whitt. Both are deceased. Today, authorities announced that thanks to modern DNA technology, they discovered remains found years ago belonged to Bobby. #ABC11: https://t.co/msNJJHK6Zn pic.twitter.com/1rAqifIUts— Gloria Rodriguez (@GloriaABC11) February 5, 2019
Investigators said he confessed to both murders.
"You are supposed to protect your children from the monsters and I don't know when it is that he became the monster," Mosteller said.
Mosteller and her mom, Barbara Moellmann, are remembering Myong and Bobby, who was only 10 years old when he died.
"He was so sweet," Mosteller said. "He loved video games. He loved playing air hockey. He had an air hockey table in his bedroom."
"He was a sweet, sweet, gentle, kind-hearted little soul," said Moellmann, Bobby's aunt, to ABC affiliate WCPO.
"He was a good little boy. There are no words to describe what this has been like for our family. This has been the most tragic, devastating experience of our lives."
Mosteller has set up a GoFundMe page.
She said they're raising money so they can bury them in Ohio with Bobby's grandmother.
Here is a full statement from the family:
"Our hearts are broken into a million pieces. We had no idea that Bobby and Myong Hwa were no longer with us and had not been for a very long time.
It came as a total shock to us when we spoke to Major Horne. Our world fell apart.
We don't think we can ever forgive our brother for what he did.
Bobby was the sweetest, kindest, and funniest little boy. He always had a smile on his face and a twinkle in his eye. And to think of that being snuffed out brings a chill to our hearts.
Our brother told us Bobby's Mother, Myong took him back to Korea to raise him and we believed him.
Now we need to bring him and his Mother home where they belong and bury them next to his Grandmother who adored him.
We would like to thank the Orange County Sheriff's Department and most especially Major Tim Horne for his 20 plus years of of work and never giving up hope and finding Bobby's Family.
The Family would like this time for privacy and to grieve."