Beyoncé Knowles becomes "a crazy person" if anyone criticises her sister.
The former Destiny's Child star is very close to her singer sibling Solange, 26.
As the older one, 31-year-old Beyoncé has always taken her duties as a sister very seriously.
"I'm a crazy person if anyone says anything about my sister," she admitted to Britain's more! magazine.
"I don't even know what happens to me. I completely turn into a lunatic... I was taught the importance of being a sister and my sister looking up to me."
As well as being close to her biological family, the star has a tight bond with her Destiny's Child friends Kelly Rowland and Michelle Williams.
Beyoncé has nothing but fond memories of her time in the band.
"They were my family... We needed each other so much," she reminisced.
"And we were super tight. We could walk into a room and not give each other the key and sing in perfect harmony... it gives me chills... that unity, that sisterhood, it is how I grew up. We slept as little nine-year-olds in the same room."
The Bootylicious singer now has her own family with rapper husband Jay-Z and their daughter Blue Ivy.
The couple married in 2008 and are still blissfully happy together.
"We have such a natural chemistry and a genuine relationship and it's based on the things that relationships are supposed to be based on," she smiled.
"People just think, 'Oh how glamorous, two celebrities are together.' No, first of all, a relationship takes a lot of work, but you have to work on yourself... you have to make yourself happy."