I'm thankful you are concerned about your family's spiritual welfare, for nothing could be more important—or more lasting. Perhaps your question will cause other readers to think about this in their own lives.
After all, one of the most important questions we can ever ask ourselves is this: How will others remember us once we're gone? Will they simply have a few kind memories about us? Or will they remember that our primary goal in life was to "Love the Lord your God with all your heart and with all your soul and with all your strength and with all your mind ... (and) your neighbor as yourself" (Luke 10:27)?
Undoubtedly, your family already knows you are a believer, and some may even admire you for it. They also probably sense that Christ is important to you and has influenced your life. But they may not realize just how much He means to you—and how deeply you wish He meant the same to them.
Ask God, therefore, to help you find ways to let them know what Christ has meant to you. For example, you might write a personal letter to each of them, letting them know of your love and expressing the hope that they will give their lives to Christ. In addition, consider planning your memorial service, to make sure it points to Christ and the hope we have of heaven because of Him.