"It was an absolute no-brainer for [Sebastian and I] to be here," said the Australian.
For non-English speaking, I was always wondering about those  brackets. Never understood the rules how they are used or what do they mean?
I always thought it's what's not said in quote, but is added there by editor for avoidance of doubt. However, the sentence without bracketed part doesn't make too much sense?
Thanks for clarification!