They care about an ethereal being that has not yet even started to exist ?

Couldn't they care about something before it comes into existence?

so surely they must not care about something that doesn’t exist

I don't understand how you arrive at this outcome that you cannot care about something that doesn't exist. Lower stakes example: gamers cared about GTA 6 before it came out. People care about future entries into game series that haven't even been thought up yet.

People care about the concept of things that don't exist enough to make them want to exist.

did they ask the future kid’s soul if it want to come into existence?

If you believe in souls, and believe they exist before birth, then I'm curious about why you think it would be selfish to bring souls to experience the mortal plane of existence. Would it not be a function of a soul to be brought here?

Cause before they conceive the child, the child doesn’t exist

According to this thought experiment, their soul exists but they don't? They meaning their physical body? I guess that makes sense.

But still: people can care about things that don't exist yet.

Just in case it isn't clear: none of the above is said with any animosity, and I'm not talking down to you.