How can one deal with a nine-year-old sister to encourage her to pray after she has started to become lazy about it and lies concerning its performance, and what is the best way to deal with a father who has suddenly stopped praying?

The matter of the nine-year-old sister is easier, as she is at an age of learning. Therefore, continue advising her, encouraging her to pray, warning her about the Hellfire, and utilizing appropriate da'wah methods. As for the father, his abandonment of prayer is a catastrophe and a major sin; indeed, his very Islam has become a subject of dispute. He should be advised to strive in supplicating for him during times when prayers are answered, and to continue advising him and reminding him of Allah and His punishment with gentleness and leniency.