The Disability Benefit is available to CPP contributors who are under the age of 65, and have a "severe and prolonged" mental or physical disability, which makes them unable to work at any job on a regular basis. A monthly benefit may also be available to their dependent children. See Benefits for children under 25 on the Canada website.
You can estimate the Disability Benefit available to you by referring to your Statement of Contributions, which is accessible online via Service Canada. You can also request that the statement be mailed to you. See also the information on the Child Rearing Drop-out Provision, which could help you meet the contributory requirements for a disability pension.
Your CPP disability benefit will automatically be changed to a CPP retirement pension when you turn 65. You cannot receive both a CPP retirement pension and a CPP disability benefit at the same time. If you are under 65, have been receiving a CPP retirement pension for less than 15 months, and you are eligible for the disability benefit, you can request to have your retirement pension replaced by a disability benefit. See the Service Canada Disability Benefit page for more information.
Self-employed and filing a tax return more than 4 years late? This affects CPP.
Canada Pension Plan Disability Benefits - Overview
Benefits for children under 25