Well, both Infamous Quests and Crystal Shard originated from the AGDI forums, which was a pretty important gathering spot for Sierra fans back in the 2000s. Back then, it wasn't unusual to see a lone graphical artist, coder or idea guy announce their own remake projects, due to the number of fans who got inspired by AGDI's remakes to create their own remakes/fangames to Sierra/LucasArts franchises. Some of those fans would be recruited by AGDI to help them work on their many projects, some would band together and join forces in attempt to complete their own project. And while the folks at Infamous Quests (known as Infamous Adventures back then) and Crystal Shard kept trudging along until their respective games finally reached the finish line, most of those other teams petered out a few months or years later, and a lot of people learned the hard way that talented people are a rare sight, so are motivated people, and that people who are both talented and motivated are even rarer. So I am not surprised there was some cross pollination between these projects due to the talent and motivation it requires to bring this kind of project to completion, and the relatively few people who have that kind of talent and motivation, and due to the fact most of the people on these teams met one another one that forum.
If I recall correctly, A Tale Of Two Kingdoms, by Crystal Shard, started out as a King's Quest fangame originally announced on the AGDI forums, but the original designer left and the remaining team members repurposed it into an original adventure game. As for Heroine's Quest, it originally started out as a solo project by Corby, but he shelved his project for several years before he gave it another shot, that time around, it attracted Pieter's attention and he lend Corby a hand to bring this baby to completion. I recall seeing both announcements to Heroine's Quest back when I used to visit the Adventure Game Studio forums, and I recall not being wow'ed by the original announcements, but quickly the graphics and animations got amazing pretty fast and the screenshots teasing it was going to be like Quest For Glory got me irrevocably hyped for the game.
As for the guys at Infamous Adventures/Quests, they started out as a bunch of goons on the AGDI forums, I recall that huge Quest for Infamy thread on the forum where they kind of pitched the game and threw around gameplay, plot and setting ideas for a game that kept getting bigger and bigger and more ambitious as days went by. I also recall them teasing us with a huge "Let's Remake the Space Quest II backgrounds" thread where tons of would-be and future background artists kind of joined forces together, one posting a preliminary sketch, then another guy would color it, and another would shade it, and another would do another pass on it, pushing pixels around... slowly but steadily remaking several of the locations from the game. Considering back in the days AGDI had revealed they intended to remake Space Quest II but canned that project because another guy announced he was doing the same, then learning that guy in question abandoned his project a year or two later, seeing those gorgeous backgrounds of Labion or Vohaul's asteroid was both amazing and gut wrenching at the same time.
Then one day these guys announced they would remake King's Quest III, as a practice exercise, before tackling on Quest for Infamy, and once they were done with King's Quest III they announced they would remake Space Quest II too, and at some point in the production of these two games, Quest For Infamy was shelved due to how huge and unrealistically ambitious the design had become. They were working on a King's Quest fangame when they decided to go commercial with Quest For Infamy, and lot of that King's Quest fangame assets was recycled into their Order of Thorne games.
Speaking of cross pollination, Brandon Blume contributed to the soundtrack of AGDI's Quest for Glory II and King's Quest III remakes, composed most (or all?) of the soundtrack of Mage's Initiation (AGDI's second commercial project), but also composed some tracks for Infamous Adventures' Space Quest II remake. Similarly, renaissance man Chris Ushko, the guy behind the Space Quest: Incinerations fangame, did a whole lot of work on the Space Quest: Vohaul Strikes Back fangame, and amazingly enough, one of the endings of Vohaul Strikes Back was designed to segue into Incinerations. I also believe one of the coder of Vohaul Strikes Back is now working on Space Venture, that spiritual sequel to Space Quest by the Two Guys from Andromeda. And last but not least, Sierra veteran and all around cool guy Josh Mandel, who voiced King Graham in Sierra's King's Quest V and VI, agreed to lend his voice to King Graham for the remakes of King's Quest I, II+ and both AGDI's and Infamous Adventures' remakes of King's Quest III.
