"Duck Dynasty" stars John Luke and Sadie Robertson teamed up recently to create a YouTube video encouraging men to be more respectful of their siblings and other women.

"That's my challenge to you, to all the guys who are watching," says John Luke. "To be a man, it starts with yourself. If you can't be a man to your own family, you're not going to be a man to those outside your family and future wife. It starts with your family."

John Luke and Sadie admit that they used to fight like "cats and dogs," and they hated each other's guts. One time, Sadie even sneaked into her brother's room and accidentally broke his eagle. John Luke got so upset with Sadie that they didn't talk to each other for a whole year.

Sadie even confesses to punching John Luke on the face inside the church once for being "annoying," simply because he was singing off-key. John Luke and Sadie's fights and arguments might have spiralled out of control, had John Luke not stepped up and took on the role of protector for his younger sister.

"It's my job to protect her, stand up for her, and watch out for her. I had to change my thinking about who she is and what she meant to me," he shares. "In the bigger sense, that's the challenge to all guys. To treat [women] like you're supposed to treat your sister."

Because of John Luke's positive relationship with Sadie, taking care of his wife Mary Kate now became second nature to him. Sadie says it's all thanks to the teachings of their mother Korie, who told her brother: "You treat that girl like you treat your sister, because once you treat your sister with that love and respect for her, it's easier to treat other girls like that."

"It's kind of like when people say you have to respect yourself before you can respect others. You have to respect your family before you can respect others," Sadie explains.