Use relationships to exploit. So many parents, siblings do it. They will never do their part but will always use it as leverage. Especially if the other person is weak in that section, is of dutiful type.
These people will always directly or indirectly remind their free of cost slaves about duties and other nice things. Will forget its spelling when their turn comes. Or if they are even more shrewd they will let others say those words for them.
“Ah! You should care more for your parents! They took care of you when you were young! They doted after you and pampered you… and now it is your turn!” as if these people were there when your parents were bringing you up, watching every step!
“It is your duty to stand by her, she is your sister! That is what siblings do, should do!”
“He is your own blood! Your own brother! You should be ashamed! How could you not take care of him?”
These people preach because they don’t have to suffer, the shrewd manipulators let them speak on their behalf and make their victims work.