Is it permissible for a sister to wear a short dress that reveals her knees in front of her brother, or to show her thigh, or to wear trousers that delineate the major 'awrah?

It is forbidden for a woman to uncover her thigh or any part of it in front of her mahrams, by agreement of the jurists. As for what is above the navel and below the knee, they differed on it. The preponderant opinion is the permissibility of uncovering what is commonly visible, such as the face, head, hands, and feet. However, it is not permissible to uncover the chest, breasts, abdomen, and back. It is stipulated that the gaze must be without lust and that there is no fear of fitna (temptation); otherwise, looking is not permissible. What is forbidden to be uncovered is also forbidden to be displayed or made prominent through tight or transparent clothing.