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A photo showing the reaction of a 3-year-old boy to finally being adopted after more than two years in foster care is going viral.

The boy, Michael, was adopted Tuesday morning in Phoenix.

His new sister, 17-year-old Dea Brown, tweeted out pictures of the happy boy, television station KPHO in Phoenix reported. They were retweeted more than 55,000 times in three days.

Mom Tara Montgomery told ABC News that Michael had been living with her family for nearly two years.

“Michael was placed with us on Feb. 14, 2015, when he was 18 months old. We were his third foster family,” Montgomery said. “His original case plan was reunification with his ‘bio-mom.’ When that plan failed, a new plan was set.”

Montgomery said that, as a single parent, she was not initially looking to adopt Michael, just to help him. She has three daughters — ages 23, 17 and 16, KPHO reported.

She told the station that Michael is “just what (her) family needed.”

The pictures tweeted by Dea Brown were taken right after the adoption became official.

“This photo is the definition of his personality,” Montgomery told ABC News. “He couldn’t help but let everyone know that he was being adopted today. We are so happy to have Michael in our lives.”

She told KPHO she’s pleased her daughter’s tweet has drawn so much attention, saying she hopes it encourages more families to adopt.

“If you are thinking about it, just do it. The impact you are making will last a lifetime on the child,” Montgomery said.