If you would like to confirm that you are the father of a child, here is a sample letter acknowledging paternity.
To [Recipient name]
Dear, [Recipient name]
I, [Name] of legal age, [Citizenship], and presently residing at [Address], do hereby depose and state that I am the biological father of [Name] who was born on [Date] at [Time].
I hereby acknowledge my paternity to [Name] and recognize them as my child and legal heir. The facts of the birth of my child were registered as required at the [Location]. I further declare that I agree to support my child and allow him/her to use my surname. I hereby agree to a custody agreement determined by the respective institution.