What is the sister brand of Uniqlo in Japan?

Excuse me, could you please clarify something for me? I've been reading about the popular clothing brand Uniqlo and I'm quite curious. Is there a sister brand of Uniqlo in Japan that operates under a different name but shares similar values or business practices? I'm trying to get a better understanding of the company's portfolio and any other brands that might be associated with it. Thank you in advance for your help.