Even with DNA proof that is not my child?I thought it meant biological child.
https://www.canada.ca/en/immigration-refugees-citizenship/services/application/application-forms-guides/guide-5289-sponsor-your-spouse-common-law-partner-conjugal-partner-dependent-child-complete-guide.html#obligations
Length of undertaking
Your obligations as a sponsor start as soon as the undertaking is in effect. If you change your mind after you submit the sponsorship application and undertaking, you must write us a letter
before a final decision is made on the file and submit the letter as an attachment through the
IRCC Webform. You can only withdraw an undertaking if we approve the withdrawal. See Step 6 to find out
where to mail your letter.
The length of undertaking for residents of Quebec is different from the length of undertaking for the rest of Canada. For more information about sponsoring a family member in Quebec, see detailed information for
length of undertaking for residents of Quebec.
For sponsorships in all parts of Canada except for Quebec, the information below explains how long your undertaking will be valid.
You’re sponsoring a spouse, common-law partner or conjugal partner
Length of undertaking is 3 years from the day your spouse, common-law partner or conjugal partner becomes a permanent resident.
You’re sponsoring a dependent child over 22 years of age
Length of undertaking is
3 years from the day your
dependent child (or the dependent child of your spouse, common-law partner or conjugal partner) over
22 years of age becomes a permanent resident.
You’re sponsoring a dependent child under 22 years of age
Length of undertaking is 10 years from the day your dependent child (or the dependent child of your spouse, common-law partner or conjugal partner) under 22 years of age becomes a permanent resident, or until the child becomes 22 years old, whichever comes first. The
length of undertaking for residents of Quebec is slightly different.
All the red text applies to your situation, the enlarged, underlined, section specifically, to your question.
Note that it's now 25, not 22 years. However that is not relevant to your situation anyway.