I am a 12 year old bpy that baths with his 10.year old sister. I asked mom if I could bath separately and she said that I could if I do my chores. On days my chores are done I can bath alone, if I leave some undone then I bath with my sister.

It's great that you're communicating with your mom and setting boundaries for yourself. Taking a bath alone can provide some privacy and personal space, especially as you both are growing up. Just keep up with your chores, and you can enjoy your alone time in the bath when you earn it! If you feel comfortable, you might also consider discussing your feelings with your mom to see if there are any other arrangements that could work for everyone.