The boys were returned to their American-born mother after Russian authorities co-operated with a UK court order for the first time and upheld the 1996 Hague Child Protection Convention.
Eight months ago, a Moscow City Court ordered Mr Neustadt to return his sons to their mother, who lives in Hendon, north-west London.
Mr Neustadt, 37, defied the order and went into hiding. This month, the children were found in a Moscow apartment with their paternal grandmother Irina Mogilevsky.
The boys have now been reunited with their younger brother Meir, who is two-years-old.