guardians; parents
Refers to parents or guardians, especially in school contexts such as 父兄会 (parent-teacher association).
We discussed the school's new policy at the parent-teacher meeting.
father and older brother
Literal meaning of the kanji; rarely used in modern Japanese outside historical or literary contexts.
In classical texts, 父兄 can literally refer to a father and an older brother.
Many parents attended the sports day.
The school contacted the parents to explain the situation.
Parental permission is required for the off-campus study trip.