How can I deal with my family members who commit some unlawful acts at home, such as not observing the hijab, having a satellite dish, and being negligent in prayer, knowing that I lack the courage and sufficient knowledge to advise them?

Your duty regarding the prevalent objectionable matters in homes is to offer advice to your family with patience and gentleness, while frequently supplicating for their righteousness and steadfastness, and adhering to the etiquettes of giving advice: purifying your intention for Allah, choosing the best methods and means, seeking out appropriate times, selecting the kindest words, and avoiding public admonition.