Do you have any family or children in the UK?
What nationality is the mother?
Are you and the mother in a relationship?
If your partner is a Latvian National and you have a child together, based on the information that you have provided above and without seeing any documents, I would be of the opinion that you would be eligible to apply for an EEA Family Permit as the partner of an EEA Citizen. You would have to show that you have been in a subsisting relationship for at least 2 years.
An application would have to be made to the Home Office.
I hope this answers your question. If so, kindly rate the answer and provide feedback.
If you have any further questions, please do not hesitate to ask.