Can one retract the intention to donate for the sponsorship of an orphan (with money that was designated for buying cigarettes), and use these funds to help the father, knowing that the sister was already helping the father?

The vow must be fulfilled if the questioner vowed to donate the money he used to spend on cigarettes to sponsor an orphan, because the Prophet, peace and blessings be upon him, said: "Whoever vows to obey Allah, let him obey Him." A vow is only binding through verbal utterance. The questioner can be kind to his father by gifting him some money, and if the father is in need, his maintenance is obligatory upon his children.