Is the white cat that appears on the doorstep and is associated with the father's distress harmful, and how can it be driven away, and how can one ascertain whether the father is ill or not, and what should be done in this case?

The parent's irritability or nervousness may not be related to jinn or magic. One should not rush to interpret events as magic or possession to avoid delusions. Medical or psychological causes for nervousness should be sought and treated. If there is a strong suspicion of magic or possession, the treatment is through ruqyah shariyyah (Islamic exorcism). It is important to fortify homes by remembering Allah, reciting the Quran, especially Surat Al-Baqarah.