The Prophet (peace and blessings be upon him) said:
"Whoever comes to own a relative within the prohibited degrees (mahram), that relative becomes free."
Hadith Referenceصحیح الجامع الصغیر / حرف الميم / 6557
Hadith Gradingالألبانی:صحيح
Hadith Takhrij[حم د ت هـ ك] عن سمرة. الإرواء ١٧٤٦.