Hey, Summer Memories got an official shout out on their twitter once, someone must have a real weak spot for that one at valve.

It looks like the affected games are all rated "Adult Only" on Steam.

The games you mention are all sold without adult content on Steam, and the customer has to visit the publisher's website to download a patch restoring said content

They went after incest and non-con (for now).

But I don't know about the last game you mentioned... the "sister" part sounds sus.