(a) Civil marriages prohibited by law on account of consanguinity or affinity between the parties or on account of either party having a wife or husband living, if solemnized within this State, shall be void without decree of divorce or other legal process.
(b) When the validity of a civil marriage is uncertain for causes mentioned in subsection (a) of this section, either party may file a complaint to annul the same. Upon proof of the nullity of the marriage it shall be declared void by a decree of nullity.