Al-Jawab Billahi At-Taufeeq (the answer with Allah’s guidance)
Allah Ta’ala says,
“They (believing women) must not display their beauty except to their husbands, their fathers, their husband’s fathers, their sons, their husband’s sons, their brothers, their brother’s sons, their sister’s sons or their women
The Awra of a woman in front of her Mahram men (those with whom marriage is permanently unlawful), such as the father, brother, son, paternal uncle (father’s brother), maternal uncle (mother’s brother), father in-law, grandson, husband’s son (from another marriage), son in-law, etc consists of the area between the navel and knees, and also the stomach and back.
Thus, it will be permissible for a woman to expose the following parts of her body in front of Mahram males: head, hair, face, neck, shoulders, hands, forearms, and legs from below the knees. It will not be permissible to expose the stomach, back or any area which is between the navel and knees. (Al-Fatawa al-Hindiyya, 5/328 & al-Hidaya, 4/461).
Exposing the chest is not advisable, and is disrespectful for women to expose the upper part of their chest just below their neckline to their Mahrams.
Also, it is not permissible to wear see through clothes for women that doesn’t cover their Awrah (which is mentioned above) in front of their Mahram males.
However, it should be remembered that if there is a fear of temptation (Fitna), then it will be impermissible to expose these parts even in front of Mahrams, neither will it be permissible to see those areas of a Mahrams body. (Al-Lubab fi Sharh al-Kitab, 3/218).
And Only Allah Ta’ala Knows Best.
Moulana Qamruz Zaman