translation - This mother doesn't know her own child?

I have the following sentence in my JLPT practise book:

当時{とうじ}母{はは}がどんな気持{きも}ちだったのか、子{こ}どもの私{わたし}には知{し}るべくもないことだった。

My faltering translation is something like, "How did my mother feel at the time, she couldn't have known it was me."

I'm unclear on the implications. It seems to be that the mother's feelings are unclear because of not knowing who the speaker is, but who the speaker is and how the mother would express it don't seem logically related to me. For example, if she shouted because she was angry, it wouldn't matter who she thought she was shouting at for an outside observer to determine she was angry.

How does knowing who the speaker is and her feelings at the time connect? I feel because I don't have a logical interpretation of the implications, my translations doesn't feel correct.

What would be a more accurate translation than mine?

Answer

It seems you're not interpreting the sentence quite correctly.

It should be "As a child I had no way of knowing how my mother felt at that time."

[当時]{とうじ}[母]{はは}がどんな[気持]{きも}ちだったのか

Would be "how my mother felt at the time."

[子]{こ}どもの[私]{わたし}には[知]{し}るべくもないことだった。

I think this is where you might be getting thrown off. 子供の私には is what you need to focus on. 子供の私 is the "child version" of the speaker, from that point in time. には is saying that the preceding is not comprehensible to him/her. I assume べくもない is the target grammar point so you should know that it's saying, basically, "had no way of knowing."