Three sisters are forced to join forces when Alzheimer and stroke hit their family and they need to take care of their parents while learning all about motherhood, forgiveness and the true meaning of happiness

Rose,

Three sisters forced to join forces sounds weird. They are already family. I would reword this to describe what sacrifices they are making by coming together.

Otherwise, this sounds like a theme you can explore in various, humanistic ways. My only suggestion is to be sure you have a clear protagonist, because studios and gatekeepers often look for it in a story.