Disclaimer: The Twilight series is not mine, it's Stephenie Meyer's.
I'm making my own theory to why Jacob is still the same.
Jacob POV:
Carlisle, Edward, Emmett, Jasper and I were discussing the baseball game, for at least two hours, but two hours means nothing to any of us, we have as many hours that we need. Anyways, about two hours after discussing the game Carlisle said to me, "Jacob, I think I have a theory of why you're not aging."
"What's the theory?" I asked.
"I'm still testing the theory, but I'll let you know, if it's even possible," Carlisle said while starting to flip the channels on the television.
"Edward?" Edward would know the theory if it was in Carlisle's head.
"Sorry Jacob, Carlisle is hiding it." I could tell Edward wasn't lying, this time.
After that, we all just stared at the television, until the others came, and started telling us their ideas for the yard.
Alice POV:I could tell that our idea for the pool would work, so we decided to go let the others know, so they could start helping us construct it.
"We've decided that we're going to make a huge backyard," as soon as I said huge Edward and Jacob looked at Bella to see what her thoughts were of the idea, "we'll place a pool, so when we have guests Edward and Bella can invite them over."
Edward thought for a moment, I knew what his answer was but I waited for him to respond, "That's a great idea!"
"When are we going to start building this big backyard then?" Jacob asked, not that interested.
Edward and I both said at the same time, "Tomorrow." Jacob sighed, because he wasn't that interested in this big house that was being built. If he didn't have to bend whenever he went into their old cottage, he would've just offered to take the cottage for him and Nessie.
After all of us staring at the television for a couple of hours, Bella, Edward, Nessie and Jacob left, and promised to start building as soon as Nessie and Jacob wake up the next morning.
Bella POV:
I really like the pool idea. Since I've become a vampire, I haven't used my ability to not breathe much, so now would be my chance with the pool, to practice. Also Edward and I can react our time in the ocean when we were at Isle Esme. Edward and I enjoyed our night together while Nessie and Jacob were sleeping.
In the morning, Alice, Esme, Jasper, Emmett and Rosalie arrived with all the supplies we'd need for our pool.
"How big is this pool going to be?" I probably didn't want to know the answer to my question, but I may as well get it over with and ask it now.
"Um," Esme said thinking, "We're combining a couple of pools, so probably about five times bigger then an average backyard swimming pool." Ah! Was all I could think, I knew that everyone liked this idea, so there would be no point for me to argue against everyone.
"Where's Carlisle?" Jacob asked while trying to figure out where all the pieces go.
Edward answered, without having to think, "He's researching about what he thinks, is the reason you're still around… mutt." Edward and Jacob still aren't great friends, especially now that Carlisle has been spending most of his time working on the reason Jacob hasn't aged.
"So you do know what Carlisle thinks is the reason why I'm still around annoying you," Jacob said, while still trying to figure out which piece goes where.
"I might," Edward said smirking. Edward knows how much Jacob is curious about what's wrong with him.
By the end of the day, well for Nessie and Jacob, we decided to take a break and continue the next day. We only managed to finish the landscaping, but that's because Rosalie, Esme and Alice were inside the whole time decorating. I'm not even sure I wanted to go back into the house to see what they did to it, but I had to.
