Guevedoce children are inbetween genders and are proof that not only is gender a social construct, but we do not fully understand how the biology of sex works. Raising them as girls is confusing to them, but if there is no indication otherwise, than there can be no clear way of how to raise them genderwise.
No, the guevedoce children should not be considered to be girls. Although they appear to be female at birth and during childhood, when they reach puberty, their penises and testicles descend and they grow to be fully functioning men. They are biologically male and grow to be men. They just simply show the outward male characteristics beginning at puberty.
Puberty is a difficult time in the phase of development into mature adulthood. To begin with, we don't all look the same when we are infants. Some people mature physically faster than others. At 13, some boys are already men; some girls are already women. Either sex is biologically capable of reproducing in adolescence, even though it is not encouraged. People may continue to grow until their twenties. Therefore, at age 12, if a person always assumed to be a girl grows male genitalia, then we should consider this child a male -- or a transgendered person -- if that is what the person wants. Nowadays, society is more open to gender diversity. A person need not be afraid to claim to be both sexes. Guevedoce children could be considered to be either sex.
Johnny, once known as Felicita, has admitted that he has never enjoyed playing with toys for girls and wearing their clothes. If he is happier expressing himself as a boy, so may it be. Gender as a subject is much more complex than a simple question of nature vs. nurture, and there is no minimum or maximum age at which change can happen. At the end of the day, describing things as either one way or the other might only serve to cause harm to the people involved. I believe that everybody has the right to be considered whatever gender identity they feel most satisfied with.