Hotel buffets are shite these days, especially in Taipei. You can spend US$150+ a night and still only get a pot of shi fan, some grotty sliced bread and jam, builder’s coffee, and a few bits of fruit.
Frankly, I’d suggest you get room-only and bring your brother to a nearby cafe for breakfast. You’d need to send him to the Far Eastern or somewhere similar to get an even halfway decent buffet.
FWIW the Forward Hotel near Xinpu MRT isn’t bad, but IIRC the breakfast was only so-so.
In reality, complementary breakfasts are almost never actual free. They count it in and it’s almost always a bad deal. Including breakfasts is always a bad deal as well, they overcharge for what it is. I only get it if it’s the best option or only option.