1900 US Census St. Louis, Missouri Garrison Avenue
Lang, Michael, Head, born September 1860, aged 39, married, 11 years, born Ireland, parents b. same, immigrated 1880, naturalized, confectionary manufacturer Lang, Katie, Wife, born February 1872, aged 28, married, 11 years, 3 children born, 2 children living, born Kentucky, parents b. same Lang, Mary M., Daughter, born June 1889, born Missouri Lang, Arthur J., Son, born February 1897, aged 3, born Missouri
His death is registered in the index of Missouri deaths at the Missouri Secretary of State site. Perhaps if you order the actual registration, it may provide you with the names of his parents. Also, when and where were they married? The marriage record (especially the church record) may provide more details.
Michael's birth pre-dates civil registration in Ireland, so you will have to do some work to find out the names of his parents to hopefully find a baptism, but you'll need for info.