Step-by-step explanation:
Elie is only thinking about staying with his father as the Jews are being separated because he wants to stay with father if his mother and sisters are being separated from the boys, which is the only part of his past life that stays with him for a long part of the holocaust.
Eliezer prays that he should not do the same to his father. It is difficult for Eliezer to fight the feelings that his own chances for survival would increase without his father to support.