I'd reiterate what others have said. The Homestuck Epilogues is, moreso than Homestuck, a story aimed at adults and about adult topics in a way that absolutely makes it an 18+ story. There's a greater level of gore and sexual content, and the list of content warnings, while presented in a jokey way, is indicative of everything present in the story.

Personally, they are my favorite part of the entire series. I think they're a fascinating exploration on the purpose of narrative and "canon", they have some devastating emotional gut punches, and some fantastic character moments. I would recommend them, but even if not recommending them to someone younger than 18, I would still say to wait a bit after reading Homestuck. This is a story about the "happy ending" not actually being what the characters want. It's a story about the consequences of growing up. Giving some time, at least in your mind, the let the kids "grow up" is probably a good thing.