Iranians are Breaking Islamic Law in Large Numbers
It is illegal for unmarried couples to live together in one apartment. Sexual relations between unmarried people are illegal and are punished. Both are against the law in Iran under Islam. But, most young people under age 30 (and there are millions of them) are living together in Iranian society that is in conflict with the official rules and traditional family values. Some call it a "Social Quiet Revolution". Quiet because only the closest friends or family members that can be trusted know. Propelling this is Iran's low marriage rate and high divorce rate, there are many more single people in Iran's major cities now.
Most young couples living together do so secretly, even though the government seems to tolerate some of this because of the numbers and because there are more pressing issues than policing this social thing. The young people of Iran seem to pushing away some aspects of Islam in preference of Western social norms and the government can only do so much to prevent it. How to deal with partners living together out of wedlock is not clearly defined by Iranian law. So, that is part of the dilemma for the government.
Those breaking the law do so very carefully and watch their backs as the enter and leave an apartment building. There have been some pro-regime supporters who have reported the violators, yet nothing much done.