Complex sentence: His parents raised him as an atheist, but at the age of 20 he converted to Catholicism and was baptised in the chapel of the Sisters of Adoration on July 8th 1935.
Split into simpler sentences: His parents raised him as an atheist, but at the age of 20, he converted to Catholicism. He then was baptized in the chapel of the Sisters of Adoration on July 8th 1935.