'I just feel like more complete': Teen surprises her stepfather with legal name change for his birthday

A young woman in Oregon changed her last name to match her stepfather's.

A man in Oregon just had a birthday surprise he'll never forget, thanks to a beautiful, heartwarming gesture from his stepdaughter.

On Thursday, Giselle "Gigi" Santoyo presented her stepfather, Alfredo Santoyo of McMinnville, Oregon, with a gift that had him crying almost immediately after he pulled the tissue paper away.

At the bottom of a big box filled with his favorite snacks lay a certificate revealing that she'd changed her legal last name to match his.

"Happy birthday!" the family yelled out in video that Gigi Santoyo posted on social media.

Gigi Santoyo told ABC News that Alfredo Santoyo had raised her since she was 5 months old and that she'd wanted to graduate high school with his last name. The family includes Alfredo and Ruby Santoyo and their children, Gigi, Nadia, Alfredo Jr. and Anjelica.

Alfredo and Ruby Santoyo have been together for more than 18 years.

"Growing up, I've always wanted him to adopt me and he's always wanted to adopt me," Gigi Santoyo said.

When she turned 18 on Oct. 19, she acted fast, making sure to get her name changed in time for his birthday on Thursday. Ruby and Gigi Santoyo even made sure to get a blessing from Alfredo Santoyo's father to take the family name.

Gigi Santoyo said she was really nervous watching him unwrap the gift.

"His reaction was something I was waiting for and to get the reaction that I got, I knew I did the right thing," she said. "Now that it's legal I feel like I'm more...More a part of the family too, because now we all have the same last name...I just feel like more complete."

Alfredo Santoyo told ABC News that the gesture was incredibly touching.

"Opening up a present and seeing a legal document of her showing me that she had changed her name...It was the greatest thing, the best present I have ever had," he said. "Just seeing her reaction was just wonderful too."

He said Tuesday that he had never once considered Gigi Santoyo different from her siblings.

"The way I feel now has not changed from what it was before. It has never been any different," he said. "It has always been a great relationship...[I] wouldn't change it for anything in the world. That's our little story."