All persons in this State who, previous to their actual emancipation, had undertaken and agreed to occupy the relation to each other of husband and wife and were cohabiting as such or in any way recognizing the relation as still existing on March 12, 1872, whether the rites of marriage have been celebrated or not, shall be deemed husband and wife, and be entitled to all the rights and privileges and be subject to all the duties and obligations of that relation, in like manner as if they had been duly married according to law.
But the provisions of this section shall not be deemed to extend to persons who have agreed to live in concubinage after their emancipation.