Simplify the following text for a Grade 14 native English-speaking person.
Original: In his memoirs , Lee refers to his immigrant background as a fourth-generation Chinese Singaporean : his Hakka great-grandfather , Lee Bok Boon ( born 1846 ) , emigrated from the Dapu county of Guangdong province to the Straits Settlements in 1862 .
Simplified: Lee says in his autobiography that he is a fourth-generation Chinese Singaporean : his Hakka great-grandfather , Lee Bok Boon ( born 1846 ) , emigrated from the Dapu county of Guangdong province to the Straits Settlements in 1862 .