All I see is a big sun, or a god…A sun — and the moon!”

Austin Underwood says he has loved his fiancée, Jessica Smith, since they were 4 years old, when their mothers met at a support group for children with Down syndrome.  

Thirty years later, the Dallas couple will finally tie the knot.

“I want to marry her because I love her. She’s my very own best friend,” Austin told NBC’s Maria Shriver.

The couple have grown from being playmates to prom dates and, next month, husband and wife.

“All I see is a big sun, or a god,” Jessica said of her sweetheart. “A sun — and the moon!”

Their story reflects not only their love, but the determination by their mothers to give their children normal lives.

“’Two people with Down syndrome, they’re really getting married?’ You know, there’s a little bit of stigma still there,” said Austin’s mother, Jan Underwood. “And this is kind of another chip away of removing that stigma.”

Georgia Smith, Jessica’s mother, said that stigma began at birth.

“On the delivery table, the physician said, ‘This is a bummer. This child is a mongoloid,’” she said.

Underwood’s doctor told her something equally disturbing.

“My doctor said, ‘You know, you don’t have to take him home. Your son will never be self-supportive, he will never be self-sufficient,’” she said. But she refused to listen.

“It was like, we’re going to make this work and prove everyone wrong,” she said.

In addition to becoming friends, the two mothers became advocates for children with developmental and intellectual disabilities. They fought when their schools tried segregate their kids with other “special needs” students, insisting they be mainstreamed into traditional classrooms, where they felt expectations were higher.

“I was not going to just have a child with Down syndrome, I was going to have the best child with Down syndrome, because I’m a very competitive person,” Underwood said.

She convinced sports coaches to let Austin play on their teams. Jessica, meanwhile, starred in school plays, her love of theater and other arts encouraged by her parents.

“Everything that we like, we include Jessica, so she likes music and she likes photography,” Smith said. “We wanted to help them be the most prepared they possible can for independence.”

That preparation paid off. Austin and Jessica, now in their 30s, both have jobs, a rarity for people with intellectual disabilities, who have an unemployment rate of nearly 90 percent. The couple also live on their own, dividing household chores like any other couple: She cleans, he cooks.

Last Christmas, Austin got down on one knee to pop the question to Jessica, giving her a diamond ring that once belonged to his mother.

The couple are writing their own vows for the June wedding, which will have a Western theme to capture their love for country music.

“We both are really happy about getting married,” Austin said.

His mother sees the celebration as a confirmation of what is possible when children are empowered to dream big.

“Absolutely, because you always want the best for your children,” she said. “You want total happiness for them. And this is it.”