Complex sentence: Lemony Snicket is obviously writing to the first Beatrice (the Baudelaire mother) and this takes place before "The Bad Beginning", and evev before Violet, Klaus and Sunny were even born.
Split into simpler sentences: Lemony Snicket is obviously writing to the first Beatrice (the Baudelaire mother) and this takes place before the Bad Beginning. Actually, before Violet, Klaus and Sunny were even born.