Final answer:
The claim that John and Mark are twin epistles is false; they are actually two of the four gospels in the New Testament, written by different evangelists and symbolized by different figures in Christian art.
Step-by-step explanation:
The statement that the twin epistles are John and Mark is false. In Christian New Testament texts, epistles refer to letters, often those written by the Apostle Paul to various early Christian communities, whereas the term gospels refers to the four books that record the life of Jesus: Matthew, Mark, Luke, and John. Each of the four gospels is attributed to a different evangelist and is represented symbolically by different figures: Matthew is represented by a man, Mark by a lion, Luke by a calf, and John by an eagle, as depicted in various historical Christian art such as the Book of Kells.