I have two nephews; one is five years old and one is four; are they Mahrams (unmarriageable male relatives) to me?
Is it true that a person becomes a Mahram when he can distinguish between things like colors, tastes and suchlike or is it when he reaches puberty?
A Mahram should be pubescent and sane because a minor or someone who is insane cannot provide the protection that a woman needs. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.