Three emperors in ancient times:

Yao, Shun and Yu

Northern Wei dynasty:

Tuoba Hong, Emperor Wen of Northern Wei Dynasty

Northern Zhou dynasty:

Yuwen Yun, Emperor Xuandi of the Northern Zhou Dynasty

Tang dynasty:

Tang Gaozu gave Tang Gaozu's Zen position to Emperor Taizong Li Shimin.

Tang Ruizong gave the position of Li Dan Zen to Xuanzong Li Longji.

Emperor Xuanzong of the Tang Dynasty gave the Zen position to Su Heng.

Tang Shunzong Song Li

Northern Song Dynasty:

Song Huizong gave the Zen position to Qin Huan.

Southern Song Dynasty:

Song Gaozong Zhao Gou Zen to Xiaozong Zhao Shen

Song Xiaozong Zhao Shen Zen position gives light to Zhao Chun.

Qing dynasty:

Emperor Qianlong gave Renzong Jiaqing a Zen position in the Qing Dynasty.