Who do we call Buddha?
Dona asked this question to the Buddha in the Dona Sutta:


  "When asked, 'Are you a deva?' you answer, 'No, brahman, I am not a
  deva.' When asked, 'Are you a gandhabba?' you answer, 'No, brahman, I
  am not a gandhabba.' When asked, 'Are you a yakkha?' you answer, 'No,
  brahman, I am not a yakkha.' When asked, 'Are you a human being?' you
  answer, 'No, brahman, I am not a human being.' Then what sort of being
  are you?"
  
  "Brahman, the fermentations by which — if they were not abandoned — I
  would be a deva: Those are abandoned by me, their root destroyed, made
  like a palmyra stump, deprived of the conditions of development, not
  destined for future arising. The fermentations by which — if they were
  not abandoned — I would be a gandhabba... a yakkha... a human being:
  Those are abandoned by me, their root destroyed, made like a palmyra
  stump, deprived of the conditions of development, not destined for
  future arising.
  
  "Just like a red, blue, or white lotus — born in the water, grown in
  the water, rising up above the water — stands unsmeared by the water,
  in the same way I — born in the world, grown in the world, having
  overcome the world — live unsmeared by the world. Remember me,
  brahman, as 'awakened.'


The Buddha is the one who is awake, whereas the other unenlightened people are "asleep".

The Buddha is not an ancestor to the future Buddhas. He is able to see into future or past through some degree of omniscience, but he is not recalling them.