No other evidence shall be required to prove marriage of such husband and wife, or that such person is the lawful father or mother of such child or children than is or shall be required to prove such fact in a civil action, and such wife shall be a competent witness to testify in any case brought under this act,¹ and to any and all matters relevant thereto, including the fact of such marriage and the parentage of such child or children. It shall be the mandatory duty of each district attorney of this state to diligently prosecute all persons violating any of the provisions of this chapter (Chapter 31, Title 21 O.S.1951), and in all cases where the evidence is deemed sufficient to justify a prosecution for such violation, any district attorney who shall willfully fail, neglect or refuse to institute criminal proceedings to enforce such provisions, shall be subject to removal from office.