"We are thrilled to announce that we have adopted a beautiful young boy from China," the couple said in a statement. "We are so proud to welcome William to our family and look forward to bringing him home."
The couple had previously talked about their desire to adopt in their hit show -- specifically a child with special needs -- after their surrogate suffered a miscarriage.
"It's always been on our radar and I think it's time we start getting serious about it," Arnold said last March, joking, "If we could just adopt all the little people on the web page, we could fill the house really quickly."
Their adoption journey will be documented on the show's sixth season, which premieres April 30 at 10 p.m. ET on TLC.
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