After 832 days in foster care, 3-year-old Michael Brown was adopted just in time for Christmas, when he got the greatest gift of all: family.

Tara Montgomery had been taking care of Michael since he was 18 months old, but didn't initially intend to adopt him.

"As a single parent, I was not looking to adopt, just to help kids during transition," she told ABC News.

But after plans to reunite him with his biological mother didn't pan out, Montgomery filed for adoption papers, saying she had to make sure he would never wonder where he might end up next.

"He's been through a lot," she told CNN. "This is his third foster family, but he had been with us for so long, and he was a part of our family."

Montgomery calls Michael her "Valentine's baby" because he joined her family on Valentine's Day last year.

On Tuesday, the adoption, which Montgomery calls "meant to be," became official.

Fist raised in the air, Michael celebrated the occasion in front of a sign that reads, "Some things are worth the wait." One of his new sisters caught the special moment on camera and shared it on Twitter. Since then, the photo has garnered more than 57,000 retweets and more than 142,000 likes.

"This photo is the definition of his personality," Montgomery told ABC.

Michael already had the same last name as his new sisters, and Montgomery said people always say the siblings look alike. She said her daughters have been a big influence in Michael's transition into the family.

Montgomery described Michael as "loving," "smart" and "always smiling."

"We are so happy to have Michael in our lives," Montgomery said. "He wakes in the morning and says, 'Mom, I so happy.'"