'The Little Couple' 's Kids Are Finally Thriving After Struggling to Bond & Speak: 'We're Cherishing Every Moment'

For Dr. Jennifer Arnold and Bill Klein, seeing both of their children happy and healthy is their greatest joy.  

Photo: George Lange/TLC

For The Little Couple‘s Dr. Jennifer Arnold and Bill Klein, seeing both of their children happy and healthy is their greatest joy.

“After everything we’ve been through, it’s a very exciting time,” Klein, 43, says in this week’s issue of PEOPLE.

The couple and their son Will, 7, and daughter Zoey, 6, (who all have has skeletal dysplasia, or dwarfism) recently moved from Houston to St. Petersburg so Arnold could take a new job as medical director of John Hopkins All Children’s Hospital Simulation Center. Now, just a few months after the big change, the family already feels settled and in a “great place.”

Of course, the road getting there hasn’t been easy.

In 2013, Arnold was diagnosed with stage 3 choriocarcinoma, a rare form of uterine cancer that she developed following a failed pregnancy, just as she and Klein were finalizing the adoptions of Will from China and Zoey from India.

WATCH: The Little Couple Supertease

As Arnold underwent a hysterectomy and six rounds of intense chemotherapy, Zoey had difficulty bonding since she had been raised in an orphanage with no exposure to other little people.

“She really wanted nothing to do with us,” says Arnold, 43.

Will also faced his own set of challenges. “He had hearing difficulties and has undergone surgeries,” Klein says.

Despite the obstacles, their children are now adjusted and happy, and the couple is blown away by the progress they continue to make.

“They’re getting to an interesting age and finding their real passions,” Klein says. “They’re really into artwork right now, their verbal skills continue to surprise me, and they’re doing so well in school. It’s fun to watch them grow.”

The Little Couple airs Tuesdays at 9 p.m. ET on TLC.

For more on Dr. Jennifer Arnold and Bill Klein pick up the latest issue of PEOPLE on newsstands now.