At what point do you think a mother should stop seeing her son naked/ vice versa?

My mother (45f), still allows her son (12m) to walk around the house naked as well as see her naked. As the oldest daughter (13+), I feel as if this behavior is disgustingly and intolerable, even I have to see my younger brother naked, and when I avert my eyes and tell him to dress himself my mother gets mad! Just today she washed him because he recently broke his arm. His other arm is fully capable of washing him, I see no reason why she should have to wash him. And even worse, he parades throughout the house naked, clapping his balls together, and even touched his penis in front of the rest of my family. Please let me know any ways you think I could change their habits 🙏.