To everyone talking about cloth nappies: you're insane. You do it for 3 years. Then do it for another 3 years. Then talk. They are a fecking nightmare to manage.
Anecdotal of course, but they all were toilet trained before other kids. Whether that is because it is more noticeable the nappy is wet and uncomfortable or other factors (wife was home all the time, kids in a nursery from a young age all day seemed to lag further behind). But I think the cloth nappies definitely played a part.