How can one deal with brothers and sisters who do not observe prayer and dhikr, listen to music, and watch TV series and movies, while the mother opposes a strict upbringing?

Kindness is required when dealing with siblings. Advice should be given with wisdom and good counsel, and by using means of encouragement. Care must be taken to keep them away from bad companions and to provide them with good company. It is not permissible to harm the mother by hitting the siblings; rather, there are other ways to deal with them. Praying for their righteousness and guidance contains much good.