@agarwal-aarti,
agarwal-aarti wrote:Because incest is not an issue in gay marriages -- that means it would be illogical not to allow marriages say between two sisters, two brothers, and even likes between a mother and a daughter. So should all incest related restrictions which are applicable to heterosexual marriages not apply to gay marriages?
Of course not! Incestuous couples cannot legally marry because the state expects a higher rate of hereditary illnesses from their offspring. Because same-sex incestuous couples don't have this problem, the state has no reason to outlaw them.
agarwal-aarti wrote:If the above mentioned restrictions do not apply to gay marriages, then it would be discriminatory to keep applying those to heterosexual marriages.
Not necessarily. The principle of non-discrimination requires that the government treat people in similar circumstances similarly. But if one class of people can produce genetically defective offspring and the other can not, they are not in similar circumstances, and the principle doesn't apply.
agarwal-aarti wrote:My point is that gay marriages is a drastically different concept than traditional marriages.
Then I think your point is wrong, because I don't see how. I also don't see how incestuous marriages, if legal, would be drastically different from non-incestuous ones. According to standard marriage vows, marriage is about being there for one another for richer and poorer, in sickness and in health, in good times and in bad, until death do us part. How would same-sex couples or incestuous couples be incapable of exchanging those vows and keeping them?