Holly Marie Clouse' has been found alive 40 years after she was left at an Arizona church by two 'nomadic religious cult' members wearing white robes.
Her parents - newlyweds at the time- Harold Dean, 21, and Tina Gail, 17, were murdered in January 1981 in the Texas woods.
The Texas Cold Case and Missing Persons Unit began looking for Holly after officials confirmed the identities of Harold and Tina only earlier this year.
Clouse, now 42 years old, met biological family for the first time earlier this week via the internet.
The National Centre for Missing and Exploited Children is facilitating an in-person meeting in the near future.
Clouse was raised by a two foster parents; they are not considered suspects.
An organisation set up after her disappearance, called The Hope for Holly project, spanned state lines, with law enforcement officials in Texas, Florida and Arizona working to find Harold and Tina's missing baby.
Once Clouse was found, her extended family said finding her was an answered prayer.
Donna Casasanta, Clouse's grandmother said: "Finding Holly is a birthday present from Heaven since we found her on Junior's birthday.
"I prayed for more than 40 years for answers and the Lord has revealed some of it... we have found Holly,
"Thank you to all of the investigators for working so hard to find Holly.
"I prayed for them day after day and that they would find Holly and she would be alright. Thank you from the bottom of my heart. We will be forever grateful."