Real guru is shabad guru, shabad means sound, also used for bani, word, wisdom or existence of divine itself but anyway -- 1)Caste - Gurus did not believe in caste no sane human does. 2)Gender - Gurus not being a female is not a fair criticism because anyone deserving should get the Guruship. 3)Family - It is easier for a child of a doctor to become a doctor because they have financial, educational & motivational base available. Similarly it was easier for a guru's child to be a guru beacuse they had spritiual base available/spritiual environment around them. Also some of the most evil people in sikh history have been children of Gurus themselves. 'Bhagti' or devotion towards Vaheguru is more important to guru than family.