Max Foster can't speak Korean. He's never taken down three policemen using black-belt judo skills, or traveled from Boston to Buenos Aires in two seconds flat. And he's definitely never seen holographic snakes wreaking havoc at his Starbucks. Until his scientist uncle gives him one seriously high-tech phone for his sixteenth birthday— and a mission to go with it.
I'm assuming that once Max gets this phone all the things mentioned in the paragraph actually do happen, but that's not clear yet, so this is a tad confusing as an opener. Tweaking the final phrase "and a mission to go with it" to something that links back to the wild details, would probably pull it all together and make it clear though. That sets up your inciting event. Max gets this phone, and weird things start happening.
The phone puts Max in touch with two brothers he didn't know he had living on opposite sides of the globe. A pandemic that has already claimed thousands of lives is still spreading, and according to Uncle Renard, it's up to Max, Liam, and Gabe to stop it.
The pandemic is introduced at the same time as the brothers, and that's a lot of info to absorb all at once. This might be a better spot to introduce the mission idea, woven in with the discovery of the brothers. Max finds out he has brothers, they're all getting phone and the weird things that go with it, and then they find out it's due to this pandemic. Think about the steps of Max's problem. He gets a weird phone, he finds out her has brothers, he finds out they need to do something to save the world. Things keep getting worse for Max, which is good.
[Armed with their phones,] they can travel to any city [threatened with an outbreak] using the TeleTransitSystem, and download any skill they need thanks to the handy Ad-I (Additional Intelligence) widget.
A few things jumped out at me here that interrupted the smooth flow of the writing. "Armed with their phones" made me think the phones were a weapon of some type, instead of a device that helps them. Same with "threatened with an outbreak." I suspect they go to a city that has already had an outbreak, otherwise how would they know it was in danger? I also wanted a little bit more about how this phone works. You haven't established what technological level this book is set in (though I assume modern day?) so I don't know if this is super techy or just everyday stuff. The first thing I think of is Star Trek and the Matrix, which probably isn't what you want.
But when they uncover the source of the disease, a computer program called Ofidia, the boys learn the truth...they aren't brothers, they're clones.
This is a fun twist, and I immediately wanted to know who they were clones of. I also wanted to know why they were in danger because they're clones. You do go into that more in the next para, but some sense of trouble here to up the stakes again could transition nicely in to your final paragraph. I'm also unsure how a computer program can affect people. For the clones, I suspect this is somehow tied into how they can download information from their phones (nanotech maybe?) but humans have no way of contracting a disease from technology. Unless, they too have some kind of nanotech or a way to use the TeleTranistSystem and the Ad-I widgets, then I can see how this disease could be transmitted via computer. Perhaps a little more world building here to explain how everything works together.
Ofidia, designed by a brilliant evangelist who has a bitter past with Uncle Renard, was only supposed to target clones.
Why? There's been nothing said as to why clones are bad, or even that anyone knows they exist. If they're a threat large enough to need a virus to get rid of them, there must be a lot of them and they must not be easy to find. Since an evangelist is the one wanting them dead, it could be for religious reasons, but the motives are unclear still. It feels like it needs a "but" sentence at the end here to up the stakes once again. "But now it's killing humans instead" or the like.
Now caught in a battle between the scientist that created them and the religious zealot determined to destroy them, Max and his brothers must stop Ofidia from wiping out the human race.
Is there really a battle between the two, or is this about stopping the virus? Perhaps flip these ideas, so the goal is stopping the virus, and the obstacle to that goal is the man trying to destroy the clones.
Back to you. I hope this was helpful.