§ 46–401.01. Marriages void ab initio — In general.
The following marriages are prohibited in the District of Columbia and shall be absolutely void ab initio, without being so decreed, and their nullity may be shown in any collateral proceedings, namely:
(2A) The marriage of a person with a person’s grandparent, grandparent’s spouse, spouse’s grandparent, parent’s sibling, parent, step-parent, spouse’s parent, child, spouse’s child, child’s spouse, sibling, child’s child, child’s child’s spouse, spouse’s child’s child, sibling’s child.
(3) The marriage of any persons either of whom has been previously married and whose previous marriage has not been terminated by death or a decree of divorce.