When my best friend Ben told me he wanted to marry my younger sister Rosie, I didn’t know what to say.

Rosie had Down syndrome, but she had never allowed other people’s expectations to define her dreams.

She wanted independence, a family, and someone who would love her for exactly who she was.

Ben had known our family for years. He knew Rosie’s stubbornness, her infectious laughter, and her habit of watching the same favorite movie over and over.

When he proposed, she was happier than I had ever seen her.

Their wedding was beautiful, and for years, I watched them build a life together.

Still, a question lingered in the back of my mind.

Why had my best friend chosen my sister?

Then Rosie became pregnant with twins.

At thirty-four weeks, a frightening medical emergency sent her rushing to the hospital.

As doctors prepared her for emergency surgery, Ben stood beside her bed, holding a letter Rosie had written.

And when he finally handed it to me, I discovered the answer to the question I’d been afraid to ask for years.

Continue below in Part 2