As you were not married, either of you would need to file a paternity action. A paternity case would discuss paternity, custody, support and any other related issues.
If you believe that he may not be the father, you may request a DNA test. As you may know, such a test is typically about 99.99% accurate. Meaning, you would definitely know whether or not he is the father.
And yes, based on the facts as you have described them, you certainly have a right to be involved in their lives, whether as the primary custodian or through a visitation schedule.
Please let me know if anything requires clarification.
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