Even though a person should not give advice without being asked, if he sees that his friend wants to perform an act which will certainly turn out bad, he is obligated to inform him about the bad consequences which will happen, and to advise him to refrain from this act. This obligation is included in the biblical commandment “You must not stand over the blood of your friend!”. This is even more true if one is worried that one’s friend will violate even the slightest law of the Torah, that one must inform him to keep him far away from sin.
That which we have said that one should not give unasked advice is only true when relating to a person who is not a family member. However, to one’s brother or family member one must give even unasked advice, for one cannot ignore them, as they are one’s own flesh. This is even more true for one’s descendants, that even if they have committed misdemeanors and did not ask advice, he must have pity on them like a father has pity on his own sons and advise. Lead and educate them on the straight path, so that they do that which is good in the eyes of Hashem and man, and their ways will be pleasant, which will finish with benefit in this world and goodness in the next.