Me and my sibs were all trained gently and without fuss by 22 months — but, my mom had three factors in her favor: 1) it was warm enough in So Cal to let us run about naked or
bare bottomed year - round, 2) she had a lifestyle that allowed for doing this 24/7 (not childcare / work), and 3) she didn't care if there were messes to clean up, it was all part of the progress.