For the next week or so, I got many ads on my phone about underwater packages for Hawaii, along with ads for various snorkeling and swimming gear. Now I had never researched any of that on my phone, however obviously my brother has. And the ad trackers saw that both my phone and his had communicated out over the same IP address (my parents wifi) on other random internet connections, so that is probably why they were then targeting my tracker cookie with ads that would be related to his tracker cookie. (This is all technically "easy" for the trackers to do, and seems logical that they would, because "why not").

On an unrelated note, I was making a peanut butter sandwich, started browsing some sites, and started getting ads for Skippy peanut butter. My phone must have smelled the peanut butter in the air.