It is unknown when Lady Yi entered the palace, but she became Hyojong's concubine when he was still Grand Prince Bongrim (봉림대군).
In 1649, Lady Yi gave birth to a daughter whom was given the title Princess Suknyeong (숙녕옹주; 淑寧翁主).
The King gave gifts only to the princesses as he was conscious of how the Queen would react without giving any present to the concubine's daughter.
But the Queen, who was worried about excluding Lady Yi's only daughter from her husband, personally called Princess Suknyeong with a gift.
There was a time when Lady Yi caused a great stir after calling her daughter, Princess Suknyeong, "you".