The aunt dresses before the sons of her sister like she does before other Mahrams
27-8-2015 | IslamWeb
Question:
I am married to a beautiful and obedient woman. Am I allowed to order her to wear hijab and avoid wearing makeup before the sons of her sister, knowing that they are of the same age as her and that they are familiar with each other?
Answer:
All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
Allaah Almighty says (what means): {Prohibited to you [for marriage] are your mothers, your daughters, your sisters, your father's sisters, your mother's sisters…} [Quran 4: 23] The aunt is permanently prohibited from marrying the sons of her sister as stated by the noble verse.
It is permissible for them as it is permissible for other Mahrams (permanently unmarriageable) to look at her, mix with her, stay with her in seclusion or even kiss her, if temptation is not feared. Ibn Mansoor said to Abu ‘Abdullaah Ahmad ibn Hanbal 
: “Is it permissible for a man to kiss his Mahram woman?” He said: “Yes, if he is coming back from a journey and he did not fear temptation.” He mentioned the Hadeeth on Khalid ibn Al-Waleed 
when he kissed his sister. Is-haq ibn Rahawayh said: "The Prophet, sallallaahu ‘alayhi wa sallam, did so when he arrived from a battle and kissed Fatimah." Nevertheless, he should never kiss her while hugging her or on a spot that involves suspicion, like the mouth for example, but he may kiss her on her front or head. She is allowed to display her adornment before them as Allaah Almighty said (what means): {…and not expose their adornment except to their husbands, their fathers, their husbands' fathers, their sons, their husbands' sons, their brothers, their brothers' sons, their sisters' sons, their women.} [Quran 24: 31]
Thus, you should not prevent your wife from sitting with the sons of her sister or displaying her adornment before them, unless you suspect them or fear that they are tempted by her or that she is tempted by them. In this case, you may do so. The wife should treat her husband in a good manner and avoid everything that hurts him, even if it is permissible. The husband should observe the same with his wife as well.
Allaah Knows best.