Question:
Can parents divide property among children while still alive? If yes, how?
Answer:
While alive, inheritance rules do not apply.
As long as the father is alive, he is the owner. He can give everything to one child. Or divide however he wishes. Even give everything to daughters and none to sons. While alive, inheritance shares do not apply.
After death, Islamic inheritance law applies.
While alive, it is his property. He can even donate everything to a mosque. You cannot question it. Inheritance rights begin only after death.
He should not act unjustly. Showing clear injustice will be questioned before Allahﷻ . But legally, he has full right.