The second could have the same meaning as the first, unless it was clear from other context that you were no longer a father. We are referring to a past time when it was true that he "was" a father, but he could also still be a father in the present - the sentence does not exclude that possibility. To my ear, the second is more natural even though the first makes it clearer that you are still a father.
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tostyle un"I thought you knew I was a father."The second one is used when he is no a father anymore right?No. Absolutely not. The second one is completely natural when he is still a father.
tostyle un Could you please give me many more examples?Many more? How many would you like? 50? 100? 500?
tostyle un Can I also say, "sam thought that Laura is pregnant."Please wait for one question to be dealt with before posting another.