What is the difference between 后父 and 继父? What is the difference between 后父 and 继父? Is one more formal? Is it the same with 后母 and 继母? My Mandarin textbook says 后父 is used to address your 继父.
No difference. 后X is a dialect, informal, oral word, 继X is standard, formal words.
后父 is rare, usually, you will see 后爹, 后妈, 继父, 继母.