Complex sentence: Venus and Mercury are two mutant children who are apparently under the care of Big Mama, they are one of the least dangerous mutants, they do not attack Doug while he is looking for Baby Catherine, as they are busy playing with their toys.
Split into simpler sentences: Venus and Mercury are two mutant children who are apparently under the care of Big Mama. They are also two of the least dangerous mutants, which can be noted by the fact that they do not attack Doug while he is looking for Baby Catherine, as they are too busy playing with their toys.