Andrew appeared here with the trio, Peter, James, and John (5:37; 9:2; 14:33) completing the two sets of brothers (1:16–20; 3:16–18).
The prediction of Jesus inspired two questions from the disciples. Although some scholars argue that the second question goes beyond the first in looking to the coming of the Son of Man at the end of the age, it is best to interpret these two questions as focusing on the time and the sign associated with the destruction of Jerusalem and the temple (compare 13:29–30; Luke 21:7).
These questions follow naturally from the prediction of Jesus in Mark 13:2. The disciples wanted to know the sign to have a warning so they would be ready for all these events.