This photo was taken at Vrindavan, Uttar Pradesh.

Janeu is worn both by bachelors as well as married men.

Three thread Janeu is worn by bachelors (ब्रह्मचारी) and Six thread (3 for Husband+3 for Wife = 6) is worn by married men.

(Knowledge shared and enhanced by Shiv Dayal and Ram Krishna – my friends from Vrindavan)

For more details one can read Manusmriti.

Benefits of wearing Janeu (in Hindi)