Is your father a Catholic? If he is, and also de rest of the family, it will be helpful to quote them this:
"…know that no lie is of the truth." 1 Jn 2:21
Or a very striking one that they need also to know:
"You are of your father the devil (…) for he is a liar and the father of lies." Jn 8:44
Or how will end the people that lie if they do not stop, and please notice that it is not said what type of lies: NO LIE COMES FROM GOD, whatsoever …
"But as for the cowardly, the faithless, the immoral, murderers, fornicators, sorcerers, idolaters, and all liars, their lot shall be in the lake that burns with fire and sulphur, which is the second death.” Ap 21:8
And if they object that you are exaggerating quote them this passage, where a very mild lie has taken some to their death:
From Acts 5
"5 But a man named Anani′as with his wife Sapphi′ra sold a piece of property, 2 and with his wife’s knowledge he kept back some of the proceeds, and brought only a part and laid it at the apostles’ feet. 3 But Peter said, “Anani′as, why has Satan filled your heart to lie to the Holy Spirit and to keep back part of the proceeds of the land? 4 While it remained unsold, did it not remain your own? And after it was sold, was it not at your disposal? How is it that you have contrived this deed in your heart? You have not lied to men but to God.” 5 When Anani′as heard these words, he fell down and died. And great fear came upon all who heard of it. 6 The young men rose and wrapped him up and carried him out and buried him.
7 After an interval of about three hours his wife came in, not knowing what had happened. 8 And Peter said to her, “Tell me whether you sold the land for so much.” And she said, “Yes, for so much.” 9 But Peter said to her, “How is it that you have agreed together to tempt the Spirit of the Lord? Hark, the feet of those that have buried your husband are at the door, and they will carry you out.” 10 Immediately she fell down at his feet and died. When the young men came in they found her dead, and they carried her out and buried her beside her husband. 11 And great fear came upon the whole church, and upon all who heard of these things."
Hope that all these helps. We ought to purify our hearts.
In the love of Christ and of His Word,