Apparently, the woman and her significant other had gotten into a spat over what the baby’s name would be (great tidings for what the child’s going to experience at the hands of their parents when they’re born) and she couldn’t stand to live with the guy over the disagreement.
So she moved into the same living space as her brother and OP, and that’s when problems started occurring, mainly when it came to food.
Source: https://www.distractify.com/p/redditor-kicks-out-pregnant-sister-in-law