Complex sentence: Her brothers are Phineas Flynn and Ferb Fletcher, of which she continually tries to bust because of their outrageous contraptions, but to no avail because they mysteriously disappear, which most of the time is because of Dr.Doofenshmirtz's creations.
Split into simpler sentences: Her brothers are Phineas Flynn and Ferb Fletcher, whom she continually tries to bust because of the outrageous contraptions they create. Candace never seems to bust her brothers, though because they mysteriously disappear, which most of the time is because of Dr.Doofenshmirtz's creations.