Paandu describes 12 kinds of sons - six of those who are heirs and kinsmen and six kinds of those who are not heir and kinsmen. 
1. The son begotten by one's own self upon his wedded wife; 
2. The son begotten upon one's wife by an accomplished person from motives of kindness; 
3. The son begotten upon one's wife by a person for pecuniary consideration; 
4. The son begotten upon the wife after the husband's death; 
5. The maiden-born son; 
6. The son born of an unchaste wife; 
7. The son given; 
8. The son bought for a consideration; 
9. The son self-given; 
10. The son received with a pregnant bride; 
11. The brother's son; and 
12. The son begotten upon a wife of lower caste. 

On failure of offspring of a prior class, the mother should desire to have offspring of the next class. In times of distress, men solicit offspring from accomplished younger brothers. Manu has said that men failing to have legitimate offspring of their own may have offspring begotten upon their wives by others, for sons confer the highest religious merit.
[G-1-Beginning, 1/7]

Individual judgment does not prevail the ordinances, rather ordinances prevail against individual wishes.
[G-1-Beginning, 1/9]

Kripaa said to Ashwatthaamaa - "Who lacks intelligence, and who has no control on his passions, in my opinion cannot understand the considerations of morality, even if he listens to his elders. Similarly, an intelligent person who does not practice humility, fails to understand the results of morality. A brave man, who lacks understanding, even by living under learned people, fails to know his duties. While a wise man, by waiting upon a learned person for even a moment, succeeds in knowing his duties. An intelligent person who has controlled his passions, and who waits upon his superiors, succeeds in knowing all the rules of morality, and never disputes with what is accepted by all. A person having brain disorder does not welcome soothing words. Do something only which is truly beneficial, not just to yourself only, so that you don't repent afterwards.
[G-6-War/40]

Similar words are heard from Krishn also, when Yudhishthir abuses Arjun's Gaandeev and Arjun gets ready to kill Yudhishthir. Krishn says - "Paarth, You have not waited upon the elders. You don't know the morality that is why you are acting like this. You are unable to think what you should and what you should not do. Of course, it is not easy to decide, that is why even learned people take the help of scriptures. You don't know the scriptures. You think that you know the morality and virtue but in fact you are ignorant about them. Killing a living being is sin, and saving an animal from an injury is the highest virtue. One can speak the untruth, but one should never kill. How could you become ready to kill your eldest brother who is so conversant with morality? Who is not engaged in battle, who is enemy, who is running away from the battle field, who is seeking protection, who has joined his hands, who has lost his chariot should never be slaughtered. All these attributes are in your superior. Don't rush to kill him in your foolishness without knowing morality.

You took your vow before in foolishness, and after that foolishness you are going to do another foolishness? There is nothing higher than speaking Truth, But there are some situations where speaking Untruth is better than speaking Truth. In the loss of somebody's entire property; or for the sake of Braahman; on an occasion of marriage, or of enjoying a woman, or when life is in danger; these five situations are when a lie can be spoken.  These five kinds of lies are declared to be sinless. On these occasions a lie becomes the Truth and a Truth becomes a lie. He is a fool that practices Truth without knowing the difference between the Truth and a lie. A man of wisdom, by doing a cruel act may obtain great merit like Balaak did by slaughtering the blind beast; and that a foolish and ignorant person earns great sin like Kaushik (living) among the rivers."
[G-6-War/33]

Vyaas Jee said - "There is no fault of yours in this. The deities are possessed of great Yog, they have the capability to enter other's bodies. They can get children by thought alone. They can have children by word, by sight, by touch, and even sexual union also. These are the five methods they can have children.
[G-7-Postwar/29]