Although your brother may be further away from the router, it's not just distance that matters. It's also obstructions and the environment in general. Suppose in your room you’re closer to possible interference by a neighbor w/ his own wireless router than your brother. Or suppose you have to navigate around a couple of corners and he doesn't. Suppose you’re living in a room w/ lead walls! LOL.
IOW, it's more complicated than just throwing more signal strength at the problem. More signal strength is always nice to have, but it’s not guaranteed to solve the problem if you have other non signal strength related issues. Yes, all other things being equal you would expect similar results, but that’s the problem, things rarely are equal.
FWIW, I’ve found most laptops to have better wireless performance than their desktop counterparts. In all the years of dealing w/ wireless reception, laptops just seem to be less of a problem. And I believe the reason is the antenna solution. Most place it around the screen frame which makes an almost perfect antenna. You’re using a desktop and PCIe adapter, which puts you at a disadvantage. The laptop can be easily reoriented for best reception, but the desktop is problematic. And even a slight reorientation or repositioning (even a few inches) can have a dramatic effect. Most ppl have their desktop under a desk, perhaps blocked by a desk leg, close to other electrical devices, etc. All this stuff plays a role.
That’s why I rarely use PCI/PCIe (or even USB) for desktops. Instead, I use a wireless Ethernet bridge. They’re aar more flexible in terms of orientation and placement (limited only by the length of an Ethernet cable, up to 100m). And probably better signal strength $ for $ compared to PCI/USB adapters (has its own AC adapter, doesn’t rely on the bus). Works w/ any OS, no driver compatibility issues, etc. And probably less expensive than that adapter!
[wireless router]<--wireless-->[wireless ethernet bridge]<--wire-->[desktop]