Sia was born in Iloilo City in 1977 and grew up in Roxas City, the eldest of three siblings. He was nicknamed, "Injap", a portmanteau of "Intsik" (the Filipino pejorative for a Chinese person) and "Japanese"; as his Father, Edgar Sr., is half Chinese, while his mother, the former Pacita Jaruda, is half Japanese.
Sia co-founded the barbecue chain Mang Inasal in Iloilo City in 2003. In seven years, Mang Inasal grew to 338 branches nationwide, before being acquired by Jollibee in 2010.
In 2009, Sia founded Injap Land Corporation (now DoubleDragon Properties Corporation), developer of CityMall chain of malls . In 2014, DoubleDragon Properties became a public company. DoubleDragon has been developing commercial and residential properties and reportedly plans to build 100 malls by 2020. In August 2016, the company announced it was acquiring a majority stake in Hotel of Asia, Inc.