18-Year-Old Adopted After Spending More Than a Decade in Foster Care

(INSIDE EDITION) It took more than a decade for this California teen to find a permanent family, but 18-year-old Carson Petersen couldn't stop smiling when his adoption was finalized last month.

"It's been very life-changing," Petersen, of Fresno, told InsideEdition.com.

Carson was first placed in the foster care system when he was 3 years old, after his mother took her own life. In the decade that followed, he bounced between the care of his biological father, foster care and homelessness.

Last month, his adoption with his parents Tex and Renee Petersen was finalized after living in their care as a foster child for the last three years.

"Through all the stuff I put them through, they never gave up on me," Carson said. "They always wanted me to be a part of them and they always called me their son. I let them in my heart because I know they're not going to hurt me like other families would."

Carson said he had been getting into trouble in his teenage years, like smoking and drinking, but he credits his new parents for having turned that around.

"Prior to placement with us, he wasn't passing any of his classes," Tex Petersen told InsideEdition.com. "He didn't believe in himself. He had a lot of pain, a lot of hurt. Now he sits here with me with a 3.7 GPA. He found confidence within himself."

Tex said they adopted two other children into their family, 2-year-old Joshua and 4-year-old Kaylynn.

They also have a biological son, 18-year-old Hunter. The couple had originally looked to adoption when they wanted to expand their family.

Read: Foster Parents Vow to Reclaim Girl, 6, Taken From Their Arms Because She's Part Native American

"Why have any more kids when there are so many in the world who need a fair shot?" he said. "We need to do something for these kids. They didn't ask for any of this. They didn't ask to live in a trash bag and to go home to home to home."

Carson said he always held onto hope, even when things seemed hopeless.

"You've got to always have that faith and have that hope to hang on, and just know that things are going to get better in the long run," he added.