Before you go too far remaking it for Steam, another dev was told they have the same policy (no children, even as side characters). I can't remember which game it was though. I wish you well, no matter what route you go :)
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I found it, the game is Goodbye Eternity (which at the time was called Extra Life) by RNGeusEX. The dev talks about it here:
https://the-end-of-time.itch.io/goodbye-eternity/devlog/367070/should-chiaki-bec...
I hadn't seen before, but apparently after all the work the dev put into it, he still wasn't able to get Steam to accept the game. He talks about it here: https://the-end-of-time.itch.io/goodbye-eternity/devlog/453593/fresh-news
Hopefully you are able to get it to work, or even better SubscribeStar picks up enough :)