PERRIS, Calif. (KABC) -- An infant is back with his family in Perris after a custody battle involving a surrogacy for another couple.
It all started when the surrogate mother discovered she was pregnant with two babies - and one was actually her biological child.
For Jessica Allen and her husband Wardell Jasper, there's no greater blessing than their children.
After two healthy pregnancies, the Riverside County couple decided to pay it forward, and Allen signed up to become a surrogate.
"No woman in the world should have to live their life without experiencing the love and the bond from a mother and a child," she said.
Allen was matched with a couple, and in April 2016, she said one of their embryos was successfully implanted into her uterus.
Six weeks into the pregnancy, she said her doctor noticed something rather unexpected.
"He goes, 'Well, I definitely see that there is another baby,'" she recalled. "The chance of an embryo splitting is very small, but it does happen and I just thought you know, I was very surprised."
Allen delivered what she believed to be identical twin boys via cesarean section. She said she never got to see them in person, but she was shown a photo.
"I did notice one was much lighter than the other, you know obviously, they were not identical twins," she described.
A month later, there was some shocking news. She said a DNA test confirmed that the second baby was not a twin to the implanted embryo - but actually Allen and her husband's biological son.
"I don't know how to describe it - we were floored. We were like, how did this happen?" she said.
It's called superfetation, and while rare, it occurs when a woman continues to ovulate after becoming pregnant, resulting in two babies with different gestational ages and, in this case, two different sets of genetic parents.
"He's just so smart, so intelligent, you know, he's learning fast, he's got two big brothers to run after and learn from," Allen describes her baby.
"It's an emotional situation, because you've got to think like, 'Wow, we didn't know you were coming,'" Jasper said.
Allen agreed that the entire situation took an emotional toll.
"I didn't even know I was pregnant with you," she said through tears. "I carried my own child. I didn't know he was mine."
Allen said after a complicated process, she and Jasper got custody of their son in February. Now, they say their 10-month-old boy is the piece that completes their family's puzzle.
The concept of becoming pregnant while already pregnant is not all that rare in certain animals, but in humans, it's so unusual - it happens in one in several million pregnancies. There are only about 11 case reports documented in world literature.
Perris surrogate mom gives birth to 2 babies, discovers 1 is hers