It's so rotten to have to care for your younger siblings constantly. The fact that any of the Duggar girls grew up to have their own kids at all is nothing short of a miracle. They did more mothering before age 12 than most mothers do in their first couple of years of motherhood. I know in large families, a lot of chores can fall on kids, but expecting a kid under 18 to take care of a baby while the mom is doing God knows what else is wrong, no matter how you swing it.
The mom in this story imposed one of the most unacceptable responsibilities on her teenage daughter that I can think of. She allowed her colic baby to sleep in her 16-year-old daughter's bedroom and expected her to get up with him during the night. The logic is that she (the mother) needs her sleep.
This image is for illustration only, and the subjects are models; the image does not depict the actual subjects of the story.