翻譯：我家裏有一個同父異母，但又非後母所生的姐姐。 （意思這個姐姐不是親生姐姐，又不是後面所生的姐姐。）?

同父異母的姊姊==Half sister or step sister. Yip

My step elder sister---Isn't born by my step mother too.

At home, I have a step elder sister who my dad had out of wedlock.
At home, I have a step elder sister who my dad had before my mom and his current wife.

My family has a half-sister, but non-stepmother born sister
The sister is not a natural sister, not born behind the sister

我家裏有一個同父異母，但又非後母所生的姐姐。
There is a step older sister in my home, but she isn't borne by my stepmother either.

我家裏有一個同父異母，但又非後母所生的姐姐。

I have got a step elder sister at home, she wasn't born by my stepmother also.