Your confusion stems from the fact that the present continuous tense is formed by using the verb "to be" as a helping verb, as in these examples: "I am combing my hair;" "She is washing the car." But when the primary verb is also "to be," it becomes redundant to use "to be" as the helping verb. We don't need to say "to be to be" (as in "I am being a man"); once is enough. The repetition is not merely unnecessary and superfluous, it is awkward as well. So we simply say, "I am a man." And we wind up with the present tense.
Let me put this another way: Identity is itself a continuous phenomenon. If he is my brother, he "is continuing to be" my brother all the time. His identity doesn't change; it is a continuous thing. So identifying him as my brother (merely saying "he is my brother") in the present tense is all that is necessary; the present continuous tense is not needed.
Remember, the verb "to be" ("is" and "are") signifies the present continuous tense ONLY when it is used as the helping verb.
As for putting your sentences into the present continuous tense, I hope you can now see that there is no reason to do so, and if you did, it would be nonstandard and awkward.