実の

biological; real

→ 実
phrase Uncommon #11,440
biological; real Most often used before a family member to distinguish a biological relative from an adoptive or in-law relative. In 実のところ, it means “actually” or “in fact.”
JA: 彼は私の実の兄です。
EN: He is my biological older brother.

実の父になんてことを!

How could you do such a thing to your own father!

— 崖の上のポニョ (2008)

義理の父は、実の父より良くしてくれます。

My father-in-law treats me better than my own father does.

彼女は彼の実の母です。

She is his biological mother.

メアリーはトムの実の母です。

Mary is Tom's biological mother.

彼女はその少年をまるで実の子のようにかわいがっている。

She dotes on the boy as if he were her own son.

私は彼女を実の娘のように扱った。

I treated her like my own daughter.

俺の親は―実の親じゃない本当は叔父と叔母だ

My parents aren’t my biological parents—they’re actually my uncle and aunt.

— 最強のふたり (2011)