@ Arup ji
It is not legally permissible for a married man/woman to have a live in relationship.
S.KHUSHBOO VS KANNIAMMAL
Judgment date: April 28, 2010
In appeal filed by the well know actress, Khushboo seeking quashing of criminal proceedings filed against her mostly in the state of Tamil Nadu, for the remarks made by her in an interview to a leading new magazine. The Hon’ble Supreme court opined that a man and woman living together without marriage cannot be construed as an offence.
I am taking this extract from one of the articles posted in LCI itself...
"The Apex court said there was no law which prohibits Live-in relationship or pre-marital s*x.
The Supreme court, held that Live-in relationship is permissible only in unmarried major persons of heterogeneous s*x. In case, one of the said persons is married, man may be guilty of offence of adultery and it would amount to an offence under section 497 IPC".