For this more niche fetish, I don't think there has been any sandbox or VN close to this expansive (ha ha ha). Closest sandbox games I can think of matching would be Summertime Saga, Shelter, or Love & Sex Second Base; only a select few VNs include pregnancy outside the epilogues. All the more impressive that this endeavor is done without patron support. Well done!
I only wish there was a bit more dialogue choice in how you interact with your harem members, as right now it makes the MC into a bit of a split personality weirdo. I get a lot of it is probably due to different writers for different harem girls. But, for instance, MC is quite kind and loving (albeit still sex crazed) with his sister Kazumi and with Shiori, but an asshole to his sister Kurumi. Outside family, MC is kind and loving with Hayasaki (who wouldn't be with that bundle of joy?) and even with Rumines (despite her being a huge bitch to him and slowly opening up to him), but despite them being loving toward him MC is either an asshole toward or apathetic toward Sybil, Amber and (to a lesser extent) Yurika. Like... when Sybil and Amber invited MC to their homes and really opened themselves up, come on man. Those two girls deserved some love.
I get it's a porn game, but those cold moments with Sybil and Amber sharing a narrative with extremely tender moments with Hayasaki and Shiori is a bit jarring.