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.
Firstly, it should be noted that slavery existed before the mission of the Prophet, sallallaahu ‘alayhi wa sallam; however, the Islamic Sharee‘ah cut off all the tributaries feeding into the river of slavery and widened the channels which ultimately deplete the entire river of slavery. It made the only way to enslave a free person is to take him as a captive of war. On the other hand, the Sharee‘ah widened the channels to set free the slaves who embrace Islam by obliging Muslims to free Muslim slaves as expiation for several sins as it is well-known. Thus, the only source of slavery was enslaving combatant non-Muslims who refrained from being the slaves of Allaah and chose to fight His religion. It can be seen as a punishment from Allaah for the disbeliever by making him a slave of the believing slaves of Allaah. For further information, please refer to Fataawa 85061 and 84431.
Just as it is permissible for a Muslim man to own female slaves, it is also permissible for a Muslim woman to own male slaves; however, it is impermissible for her to have intercourse with her male slave according to the consensus of scholars. Verily, this is unlawful. Al-Mawsoo‘ah Al-Fiqhiyyah (Fiqh Encyclopedia) reads, “It is impermissible for a female slaveholder to take her male slave as a sexual partner, engage in intimacy with him or allow him sexual enjoyment of her person. It does not matter whether she is married or not. This is according to the scholarly consensus, as reported by Al-Qurtubi .”
It is also prohibited for the female slaveholder to marry her male slave with a valid marriage contract. Ibn Qudaamah wrote: “It is forbidden for the male slave to marry his female owner. Ibn Al-Munthir said: ‘Muslim scholars unanimously agreed that the female slaveholder’s marriage to her male slave is invalid.’ Al-Athram reported from Abu Az-Zubayr, ‘I asked Jaabir about a male slave marrying his female owner and he said, ‘A woman was brought to ‘Umar ibn Al-Khattaab at Al-Jaabiyah, and she had married her male slave. ‘Umar admonished her harshly and was about to stone her to death; he said, ‘It is unlawful for you (to marry your owned slave).’” [Al-Mughni]
As for wearing Hijab in front of her male slaves, scholars held different opinions regarding whether the female slaveholder is obliged to observe her full Hijab in front of her male slaves and servants or should she consider them Mahram-men. Al-Mawsoo‘ah Al-Fiqhiyyah reads, “Scholars held two different views regarding whether it is permissible for the male slave to look at his female slaveholder unveiled or not.
“The first view suggests that the male slave is a non-Mahram for his female owner; it is impermissible for him to see her unveiled because he is not among her Mahram men. This is the opinion of the Hanafis, one of the opinions of the Maalikis in this regard, the less preponderant opinion of the Shaafi‘is, and one of the views of Imaam Ahmad. . . . Ibn Qudaamah said, ‘The male slave is not among the Mahram men of his female owner; it is feared that if he stayed in privacy with her, they would be tempted to commit adultery; and she is not permanently unlawful for him. He is just like other non-Mahram men. Naafi‘ reported from Ibn ‘Umar that the Prophet, sallallaahu ‘alayhi wa sallam, said: “A woman travelling with her male slave is (likely to incur) corruption.”
The second view is that the woman’s male slave is among her Mahram men; it is lawful for him to see her face and hands. This is the opinion of the Hanbalis, one of the opinions of the Maalikis, and the preponderant opinion according to the Shaafi‘is. Al-Mardaawi said, “The preponderant opinion according to the (Hanbali) School is that it is permissible for the male slave to see his female slaveholder's face and hands just like her Mahram men. This is evidenced by the following report. Anas narrated that the Prophet, sallallaahu ‘alayhi wa sallam, brought Faatimah a male slave whom he donated to her. Faatimah was wearing a garment which, when she covered her head, did not reach her feet, and when she covered her feet by it, that garment did not reach her head. When the Prophet, sallallaahu ‘alayhi wa sallam, saw her struggle, he said: “There is no harm to you. Here are only your father and your slave.” [End of quote]
For more benefit, please refer to Fatwa 92726.
To sum up, the above clarifies to the dear questioner the rules governing the interactions between the female slaveholder and her male slave; it is impermissible for him to have intimacy with her and she is obliged to observe Hijab in front of him just like other non-Mahram men. Other scholars, on the other hand, regard the male slave as a Mahram man for the female slaveholder.
Allaah Knows best.