He was born in Paranormal Activity 2. He is the son of Kristi and Daniel Rey
and apparently the first male born into Kristi's side of the family since the 1930's.
Hunter was born in 2005 as the firstborn child of Kristi Rey and the second child of Daniel Rey in San Diego, California. Hunter is first seen as a newborn being brought home from the hospital. Everything seems to be normal and positive in the house and Hunter is loved a lot by his entire family.
It isn't until he is a year old that paranormal activity begins as the demon, Toby, comes to claim the infant male he was promised many years ago. Dan and Kristi come home to a "burglary" with every room in the house destroyed, except for Hunter's room, along with the tapes from Kristi and her sister Katie's childhood along with a necklace that Katie had given to Kristi. This is when Hunter's father, Dan, has security cameras set up around the house.
Hunter's nanny, Martine, is aware of evil spirits in the house and that they are after Hunter, but Dan and Kristi fire her after they catch her burning sage around Hunter. Dan's daughter, Hunter's half-sister, discovers that on occasion a human can make a deal with a demon for wealth and power by forfeiting the life of their first-born son. She also realizes that until Hunter, there had not been a male child born into Kristi and Katie's family since the time of their great-grandmother.
As the demon continues to terrorize the house, it attacks the family dog, Abby, who watches over Hunter in the nursery at night, and gives her a seizure. Dan and Ali take the dog to the vet, leaving Kristi alone with Hunter. When she goes to check on the baby, a force drags Kristi out of the nursery, down the stairs and traps her into the basement where she is trapped for just over an hour. When Kristi emerges again, she is seemingly possessed and the next day Kristi aggressively tells Ali not to touch Hunter. When Dan and Ali review the tape of what happened, Dan calls Martine for help. Martine helps Dan exorcise the demon from Kristi and pass it onto Katie to save Kristi and Hunter from the demon. This seemingly works as the house seems to be normal again.
Three weeks later on October 9th, Katie, who is possessed by the demon that Dan transferred to her, breaks into the house killing Dan and Kristi. Katie then kidnaps Hunter who begins to cry. The scene fades to black and Hunter's crying dies down and turns into laughter.
In the ending credits it says that Katie and Hunter's whereabouts are unknown.
Between the kidnapping by Katie in the end of the second movie and the beginning of the fourth movie, Hunter becomes adopted by a family consisting of a mother and father (Holly & Doug) and their teen-daughter (Alex). He is then giving the name Wyatt.