Gigi and Bella Hadid are "not competitive at all".
The 19-year-old model insists her and her sister are each other's biggest supporters but admits people can make "mean" comparisons between them.
She said: "I just have to remind myself that she's been doing this forever. I can't keep comparing myself to her because we're so different.
"But people still love to compare and contrast us - what's better about her or what's not that good about me - and it's hard because people are really mean.
"I'm her biggest supporter, and she's my biggest supporter. We're not competitive at all."
And Bella has rubbished comparisons to 'Hunger Games' star Jennifer Lawrence, with the model insisting the pair look nothing alike.
She added to Seventeen magazine: "I never saw it. But there are some photos that it's really weird and we look very similar.
"People say it all the time. I'll walk onto set and five people will say, 'You know who you look like?' and I'm like, 'Jennifer Lawrence?' then they'll say, 'How'd you know I was going to say that?' and I'll go, 'Because I hear it five times a day.'"