According to Official Guinness Records,
The youngest person to write a bilingual book is 6 years 60 days and was achieved by Saarth Khanna Sohum (India), whose book ‘Giant Twoe and 100 Beanstalks’ was published on 2 November 2017, in Singapore, Singapore.The book is published by Sterling New Horizons Pvt. Ltd. (India).
For a complete list of 2017 records, please visit 2017 Guinness Records in Singapore.