Missing son

If someone has seen this page , please help me ,or you have some information about this ,please send to my email address : [Email caché] .My name is Nguyen Thu Nguyet ,I live in VietNam .My son is missing , he's 40 years old , left Vietnam in 1976 .His Vietnamese name is Nguyen Anh Tuan ,but i don't know his German name .Because he left with his uncle - Nguyen Minh Phu and his father -Nguyen Van Thu and his step mother -Quynh .They don't let my son know he still have one "real" mother in Vietnam for 40 years .Now his father and his uncle are living in Germany , in Kaiserstraße , 52146 Würselen, Germany
I hope someone will help me to make my son know he is vietnamese but don't know clearly about his real mother.The picture above is about his father and his step mother ,and him when he is a child .
Thank you very much