"A father can protest that his son not say Kaddish for his mother, because the father's honor comes first (Darchei Moshe 376)." http://dafyomi.co.il/erchin/halachah/er-hl-025.htm
"Question (an orphan): If both my father and mother ask me to bring them water, which request should I honor first? Answer (R. Eliezer and R. Yehoshua): Your father's comes first, for you and your mother are commanded to honor your father." "Chachamim taught that the Mitzvah to honor a father takes precedence, because also the mother is obligated to honor him." "Rambam (14): If one's father and mother both asked him to bring water, he desists from honoring his mother and (first) honors his father, because he and his mother are commanded to honor his father." "The Rivash (115) says that if a man is adamant that his son not say Kaddish for his mother, the son must obey, for honoring the father has precedence." http://dafyomi.shemayisrael.co.il/kerisus/halachah/kr-hl-028.htm
It is the mother, not the father, who carries baby for nine months and delivers birth, risking her life. Why is father more important then?