Except....
There is that post-credit scene saying they tested someone else's instead....
It is left ambiguous
There is a DNA test saying no, there is a post-credit scene saying they tested someone else by accident.
Oh I forgot about that, you're right Jaye sent one stateside because the island's DNA sequencer broke down. However, now that means nothing, they have already said the DNA didn't matter in how they would handle things, story about that on Jaye's side.
Frankly, the whole thing about everyone being hung up on them as siblings make no sense.
They're Step-siblings and it is 100% legal for them to get married. So, the whole incest vibe was off putting to me. The only incest in this VN was if you screw your aunt, and even then I can't remember if she was blood related or just a really close family friend.
I get the teasing, who wouldn't. But the whole oh my god we have to hide this because it's not right thing was kind of stupid. Being caught in the act and begging them to keep the secret of two non-blood related adults sleeping together was silly...
There are a few flaws in it, but every book has them. I find it easy to pull stuff apart being an author/editor, because half of what I do is look for the flaws and mistakes.
Again, all in all, I really liked the story.