for my mother

[azz]

Why didn't you hit your brother back when he hit you?
a. I didn't do it for my mother. She wouldn't have wanted to see me do that.
b. I didn't do it because of my mother. She wouldn't have wanted to see me do that.

Are the sentences in red grammatically correct?

 

[GoesStation]

They're grammatical, but they aren't natural ways to express the idea. Repeating I didn't do it in the answer makes it ambiguous. Native speakers would understand it as Well, it certainly wasn't because I was concerned about my mother!

A natural response begins For my mother or, better, I was worried about my mother. That answers the question that was posed.

 

[emsr2d2]

I'd reply with "Because my mother wouldn't want me to" (if she's still alive) or "Because my mother wouldn't have wanted me to" (if she's no longer alive).

 

[Skrej]

Or possibly "Out of respect for my mother."

edit: Or with an entirely different sentiment : "Because my mother would've smacked me for hitting him." :-D

 

[Tdol]

Or My mother wouldn't have wanted....