If you’ve watched the most popular videos on YouTube recently, chances are you’re one of the billion viewers who have seen a video by The Fine Brothers. Siblings Rafi Fine and Benny Fine have taken over the internet with their videos, amassing over 10 million followers since their start in 2004. The duo is best known for their popular “React” video series, which won them an Emmy for “Best Viral Video Series” in 2012.

The Brothers started the wildly popular series with the simple idea of showing viral videos to kids. “Kids React,” consists of showing a group of children a popular video suggested by fans. Following the youngsters watching the viral videos is a question portion led by the brothers, which always starts with their classic question, “What happened in the video?” Every episode of the series has surpassed one million views, and the most popular, “Kids React to Harlem Shake,” has over 27 million.

Only a year after the start of “Kids React,” the brothers launched a spin-off, “Teens React.” The popularity of the shows led to more spin-offs, “Elders React,” “Youtubers React,” and even a “Celebrities React” special that featured celebrities such as Disney actress Debby Ryan and “Modern Family” star Sarah Hyland.

Many of the videos gained popularity because of the hilarious guest reactions, such as in the video “Elders React to Nyan Cat” in which one guest exclaimed “Are you kidding me?” while another guest told the brothers the cat was her friend. But instead of just delivering comedy, the Brothers have used their fame for good causes, raising awareness through the voices of normal kids and teens.

One episode, “Teens React to Drunk Driving,” was filmed to raise awareness over the serious topic of driving under the influence of alcohol. The video is one of the most emotional in the series, and had the teen guests in tears rather than the usual fits of laughter. Many of the guests knew teens who had died, and one guest even admitted to have driven drunk before, but shared with the brothers that she regrets it.

Another video, “Kids React to Gay Marriage,” covered the sensitive topic of same-sex marriage. A group of 13 children were filmed viewing proposal videos of gay couples, followed by the classic question and answer portion. The video, which gained over 21 million views, gave children a chance to voice their opinions on the subject to a wide audience.

After creating over 200 Youtube videos, The Fine Brothers continue to deliver new videos every week. The brothers have over 10 million subscribers, and if you’re not one of them, I recommend you start watching the series, and YouTube videos starting with the hilarious episode, “Elders React to Dubstep (Shrillex).”