() are dead keys by that definition on almost every keyboard layout.
I'm Portuguese but live in the UK. The Portuguese layout (especially on macs) is dreadful for programming (because a bunch of important characters like brackets require Alt Gr to type), the UK layout sucks for writing Portuguese (because of the diacritics), so I ended up having to get used to US International as the compromise layout. I've gotten kind of used to it over the years, but the exact behaviour for dead keys varies a fair bit by platform, and especially on Linux can get quite aggravating.