If your family size changed during or since those 3 years, it could affect the amount of income you need for each of the 3 years. IRCC may also calculate a different family size for specific years based on the detailed family information you provide in your sponsorship application.I tried finding out information regarding this but no hard rock information to maintain MNI. They say they might go and reassess that income but didn’t mention it if you have already applied and your application half way through what would happen at that time. I would love to hear from person who have personally experienced this then only we can be assured about this.
but please be aware of not updating your martial information as this will affect the outcome of your application .