Your answer is yes initially is a sequence word.
Initially an octet, with seven male singers.
I would say the correct answer would be Alex is his brother since the way the statement is worded, first it talks of his sister, then of his brother Jerry and next his sibling, Alex so since it comes right after the mention of his brother Jerry I would think Alex would be a brother though I can't prove it .
Yes, you would capitalize it because it's an important noun.
