Ek main aur ek tu was a famous 1975 song from the movie Khel Khel Mein, composed by RD Burman and sung by Kishore Kumar and Asha Bhonsle.
The literal meaning of the phrase is nothing but 'You and me.' In the song this makes for the beginning of the line that says you and me, met in such a way...
Now Karan Johar is producing a movie with the name 'Ek Main Aur Ekk Tu' which will release in February 2012.