Sad story about your BIL. I hope that someday he succeeds.
Although I cannot attest to it (as I was the Queen of Queens of Day1s), from reading here on SR it seems that each quits become more problematic. Only once did I get to four days (and no Day 2s or Day 3s except for those building up to the one Day 4). It wasn't until I reached the point where a life with alcohol became more frightening than a life without alcohol.