Please help here with my brother and sister?

Talk to your mom. tell her hey im just a kid and you need to find a reliable babysitter. If your miserable just don't do it its not your job. For you sister.. that's your moms responsibility not yours but how my sister got my nephew to potty train was showing him how to use the toilet first.. constantly ask her if she has to go.. or make her go every other hour.. Offer rewards when she does a good job.