A biological (birth) parent — the parent related by blood, used to distinguish from adoptive or foster parents.
養子縁組の手続きで実親の同意が必要になる場合がある。
In adoption procedures, consent from the biological parent may be required.
彼は自分の実親を探すために戸籍を調べ始めた。
He began checking family registers to look for his biological parents.
実親と会うことは感情的に大きな出来事になることが多い。
Meeting one's biological parents is often an emotionally significant event.