当询问父母的生日时，可以使用以下英语对话：

问：

1. When were your parents born？

2. When are your parents' birthdays？

3. May I know the birthdays of your parents？

答：

1. My father was born on [出生日期], and my mother was born on [出生日期].

2. My dad was born on [出生日期], and my mom was born on [出生日期].

例如：

问：When were your parents born？

答：My father was born on August 1st, 1988, and my mother was born on May 12th, 1985.

希望这些对话对你有所帮助!如果有更多具体需求或想要更详细的对话，请告诉我。