Yes, there are quite a few. You can start by looking on popular fanfiction websites like Archive of Our Own. Just search for 'Jack Mercer Four Brothers' and you'll likely find a variety of stories with different themes and interpretations of the characters.
Common themes include the exploration of brotherly love. In many fanfictions, the love and care that the brothers have for each other are shown in different ways, like protecting one another from danger. Also, themes of growth and self - discovery are present. As the story progresses, the characters, including Jack Mercer, might learn more about themselves and their place in the family or the world around them. For instance, a story could be about Jack Mercer realizing his true potential within the family unit.
For an Alex Mercer handsome fanfic, inspiration could come from the idea of him being a sort of 'dark hero' with his looks playing a role. His handsomeness could be like a weapon. He could use it to infiltrate enemy groups by making them underestimate him. He might pretend to be just a charming guy but then surprise them with his real strength.
In a fanfic about Alex Mercer's handsomeness, the author could create some really interesting plotlines. They could describe his physical features in great detail, from his piercing eyes to his chiseled jawline. And then, they could use this handsomeness as a tool in the story. Maybe he has to charm a powerful being to get access to important information. Or perhaps his good looks are a curse in some way, attracting unwanted attention from dangerous foes.
Alex Mercer in Gears of War fanfiction could create some amazing storylines. His regenerative abilities alone would be a huge advantage in the often - brutal battles of Gears of War. Imagine him being in the middle of a fight between the COG and the Locust, getting severely injured but then quickly regenerating and turning the tide of the battle. Also, his origin story from the Prototype world could add depth to his character in the Gears of War fanfic. Writers could explore how his past experiences shape his actions in this new, war - torn universe. And his relationship with the other characters in Gears of War, whether it's Marcus Fenix or Dom Santiago, could be developed in really cool and unexpected ways.
I'm not sure specifically about the back story of 'Skylark Mercer Garland' as it could be something very specific or perhaps a relatively unknown entity. It might be a name for a character in a local story, a private project, or even a made - up name for a creative exercise.
There is no information indicating that Matt Mercer is gay. He is mainly known for his work in the voice - acting and tabletop gaming community. He has made a name for himself through his contributions to various projects, and there's no public story related to him being gay.