Are Gu and Han Yunxi brother and sister?

No, according to Yunxi's Weibo information, Gu was male No.2 and Yunxi was female No.1, and they were very good friends, not brothers and sisters. The Legend of Yunxi is jointly produced by Beijing Aiqiyi Technology Co., Ltd. and Shanghai Siba Film and Television Co., Ltd., producer, screenwriter of Jin Yuanyuan, directed by Lin Jianlun and Liu, and starring kiku.