Family

And I terrible person. So my bf has three kids and his stepmom watches them during the day and when I'm there (basically live there) she dumps the kids on me which I have no problem watching them I love them I'm just tired of her suppose to watch them and I'm doing all of it so the past week I've been waking up and leaving I feel so bad leaving them knowing there not being watched properly but I also have other things I need to do. Am I a terrible person for leaving when they should already be watched?