His brother a professor at MIT - definitely can visit relatives in US.
http://en.wikipedia.org/wiki/Roger_Y._Tsien
http://nobelprize.org/nobel_prizes/chemistry/laureates/2008/tsien-photo.html
http://en.wikipedia.org/wiki/Roger_Y._Tsien
http://nobelprize.org/nobel_prizes/chemistry/laureates/2008/tsien-photo.html