Not every killer should go to jail for life, but (let's say) some do; thus, the maximum is life. Maybe these brothers deserve 20 years, maybe they don't, but bringing people into a new country, where they will be dependent on you, in order to take advantage of them, is a serious offense. 20 years seems reasonable to me.
(Edit: changed "charge" to "offense" since that is a pattern of behavior rather than a crime.)
I'm not convinced of the value of life imprisonment (or of imprisonment). I only meant to state that the maximum sentence is not related to these perpetrators, but the worst possible perpetrator of a given crime.
(Edit: changed "charge" to "offense" since that is a pattern of behavior rather than a crime.)