One night a couple of years ago, Hannah Lucas, now 17, couldn’t shake her dark feelings. Scared and alone, she wanted to reach out to her family but didn’t know how. Luckily, her mom checked on her, and Hannah tearfully told her how she was feeling. The experience gave Hannah an idea: She’d create an app that made it easy for teens suffering from mental illness to ask for help. She asked her 15-year-old brother, Charlie, for help with the coding. Together they created the notOK app, which lets users enter contact info for up to five people they trust. If they need help, they press a button and it sends this message: “Hey, I’m not OK. Please call me, text me, or come find me,” along with their GPS location. More than 70,000 people in the U.S. have downloaded the app—and creating it brought the siblings closer together. “It was just uplifting being able to help Hannah in this way,” Charlie says, “and being able to make sure that no one else had to go through what Hannah did.”