The Sutra of Sorrow for China tells that Amitabha had no thoughts for the wheel king in his past life. He had a thousand sons, and his eldest son was nameless. He became a monk and made a vow before the Treasure Buddha, saying that if all sentient beings suffered from all kinds of distress and terror, if he could remember me and call my name, it would save them from all kinds of pains and troubles. Treasure Buddha gave him a record and named Guanyin.
Extended information:
China often uses avalokitesvara to refer to this great bodhisattva, mainly because of the prevalence of "Pu Men Pin of Hokkekyo", and Kumarajiva's translation is popular in China. The popularity of popular products was first caused by Juqu Mengxun, the leader of Beiliang in the May 4th China era, who suffered a serious illness. When all kinds of doctors failed, Dharmaksema from India advised him to recite popular products sincerely.
Ju Qumeng followed the instructions, which really made him recover without medicine. Therefore, the Lord of the country is widely popular in China. "Pumenpin" declares that if all beings recite the name of Guanyin Bodhisattva when they are suffering, Guanyin Bodhisattva can free them.