Motherly instincts?

My boyfriend and I FaceTime very often and sometimes his 7 month old brother would cry. But lately it's gone to screaming. Whenever I hear him screaming my stomach turns because his mother always yells at him! She literally won't do anything and my boyfriend will have to go get him and take care of him. Is it wrong that I feel like this? Because it's starting to piss me off Everytime he cries because she just tells him to shut up and doesn't do anything. The family is always making excuses about why she's like that " because she's always with him" but she isn't whenever my boyfriend gets home he's with him! Even when I'm there we are taking care of him. Am I wrong for feeling like this?