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Parenthood changes everything … especially when it happens unexpectedly and comes in twos.

After years of hoping to become parents and suffering through fertility issues, Bill Klein and Dr. Jennifer Arnold of TLC's The Little Couple joyfully welcomed adopted son Will from China – and now tell PEOPLE exclusively they are adopting a 19-month-old girl from India they have named Zoey.

"We're so delighted that Zoey will be joining our family and that William will have a little sister coming home very soon," Arnold and Klein said in an exclusive statement to PEOPLE.

Though Zoey – who also has a form of dwarfism like her adoptive parents and new big brother-to-be, Will – is officially their daughter, the couple is waiting on final approvals and dates to be put in place so they can bring her home to Houston.

Since they wed, Klein, 38, and Arnold, 39 have hoped to adopt a child with special needs because of their own experiences with dwarfism.

"We've dealt with prejudice and many challenges," says Arnold. "I feel very lucky and fortunate that I have the wonderful life I have."

Both Klein and Arnold say the reason they do a show is to help others understand more about dwarfism.

"A little girl came up to me in a store and said, 'You are a little person,' very matter-of-factly and I said, 'Yes, I am, thank you very much,'" says Arnold. "We have an opportunity to raise awareness and that's wonderful."

Becoming a parent, a long-time dream for Arnold and Klein, is something they say they are more than ready for.

"I wanted us to be parents before we were too old to enjoy being parents," says Arnold with a laugh.

See an exclusive clip below from their show, airing on TLC Tuesday at 10 p.m. ET where they find out about Zoey for the first time.