Girl with Down syndrome stars in brother's anti-bullying rap video

A young girl with Down syndrome is winning the internet and all of our hearts as the star of her rapper brother's new music video.

Set to Cyndi Lauper's "True Colors," the video shows Sarah Grace's peers treating her differently because of her Down syndrome, while her 11-year-old brother raps about acceptance. By the end of the video, the other girls have taken the song's lesson to heart.

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"MattyB" told Good Morning America Thursday the video was inspired by a desire for his sister to be treated fairly.

"Some people at school might pick on her for her needs," he said, "but I don't think anyone should be bullied because of what they have."

If MattyB looks familiar, it may be because you've seen one of his videos. The YouTube sensation, known for his rap covers of pop songs, has been gaining a following for years, and some of his videos have nearly 100 million views.

And how did Sarah Grace feel about being the star of one of her brother's videos?

"Sarah Grace loves acting," their mother told GMA. "She loves to be in front of the camera. She was very excited about it."

This isn't the first time Sarah Grace has starred in one of his videos, but this time it's clearly striking a chord. Posted earlier this month, the video already has nearly 4 million views.