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 facts in a civil action. In all prosecutions under this act, any existing provisions of law prohibiting the disclosure of confidential communications between husband and wife, shall not apply, and both husband and wife shall be competent witnesses to testify for or against each other to any and all relevant matters, including the fact of such marriage and the parentage of such child or children. Proof of the desertion of such wife, child or children in destitute or necessitous circumstances or of neglect to furnish such wife, child, or children necessary and proper food, clothing or shelter is prima facie evidence that such desertion or neglect is wilful.