Answer
That's a very tough position for the girls. It is very difficult to watch the ones you love reject the only savior available to mankind (Acts 4:12). Many people (including myself) come from families with one or more unbelieving parents, and the fact that we are so close to these lost souls makes their predicament very painful for us.
The fact that God chose the Jews, unfortunately, does not excuse them for rejecting Jesus as the Messiah. Rather, it makes them all the more accountable for this rejection. They have the greatest advantage in that God made incredible promises to them, and entrusted them with his Word and ministry (Rom. 3:1ff.; 9:3-5). Yet, those who have not received Jesus as the Messiah are blinded to the truth (2 Cor. 3:7-16).
Paul explains the fact that some Jews reject Jesus by saying that Jewishness is of the heart, and not of the blood. That is, one is counted as a Jew when he shares the faith of Abraham. He is not counted a Jew simply by virtue of birth. To reject Abraham's faith is to reject one's own Jewishness (Rom. 2; 4; 9). Yet Paul also offers hope that even those Jews who reject Jesus may become jealous by the fact that the Gentiles are receiving their blessings, and thus turn back to God and receive Jesus (Rom. 11).
If any person, Jewish or Gentile, dies without receiving Jesus, there remains no possibility of salvation (Acts 4:12; John 14:6). There will be no second chances after death, only judgment. The girls should not be given false hope regarding this because: 1) lies about the nature of God and salvation pervert the gospel itself; and 2) it will may make them complacent about their father's condition, so that they cease to pray for his salvation -- their ardent prayers may be an effective means by which to bring their father to faith.
The girls should also be encouraged that their youth is not a complete liability. While they may lack the learning necessary to answer their father's skepticism, they do not lack the love necessary to demonstrate Jesus' presence in their lives. They can bear witness to the truth by loving and obeying their father for Jesus' sake. Moreover, it is the Holy Spirit that changes hearts and convinces men of the truth of the gospel. Thus, no amount of learning or expertise can ever, in and of itself, bring any man to Jesus. The girls can take encouragement from this, knowing that the Holy Spirit is the one with the power to bring their father to faith. They need not rely on their own abilities. Also, as I mentioned earlier, God does answer prayer. He may not choose to save the girls' father, but through their diligent prayers God may agree to save him. In this regard, they may be encouraged to know that the unbelieving father of a friend of mine recently came to faith. His father is very old, and my friend had been praying for him since his own conversion decades ago.
Encourage them to pray, and if they are old enough that their parents will allow them, they may also want to fast from time to time as they pray. Fasting is one way that we can demonstrate our sincerity and earnestnest to God, it sometimes helps to move his heart so that he grants our petitions.
Answer by Ra McLaughlin
Ra McLaughlin is Vice President of Finance and Administration at Third Millennium Ministries.