All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
It the matter is as you mentioned in the question, that your husband has repented from taking drugs, and you have no sound reason for asking for a divorce or a khul’, then you have no right to refrain from returning to him, and your parents have no right to prevent you from doing so. He is your husband, and you are still married to him, and it is an obligation on you to obey him in what is permissible.
Your parents have no right to prevent you from going back to him, and they are wrong in doing so. So we advise you to seek the help of rational people to convince them to agree. If they are convinced, then this is what is required, otherwise, you are obliged to return even if they disagree. Please refer to fataawa 92629 and 84351.
If your family refuse to take care of your two children, then you may look for a trustworthy nursery, and the like, to take care of them.
The spouses should not be separated for such a long time; Allaah says (what means): {Then, either keep [her] in an acceptable manner or release [her] with good treatment.} [Quran 2:229]
Also, if the wife goes out of the marital home without her husband's permission and she refuses to return, then if she has no sound reason for doing so, she is sinful. The mere fact that her husband is a drug addict, and the like, is not a sound reason for refusing to return unless she fears to be harmed by him.
Finally, it should be pointed out that the illegitimate child is not traced back to the adulterer even if the latter is willing to trace him back to himself. This is the most preponderant opinion. For more benefit, please refer to fatwa 84788.
However, some scholars hold the view that if the adulterer traces back the child born out of zina (adultery) to himself, then he is traced back to him.
In any case, this is not a reason that would prevent you from going back to your husband as long as he repented and turned to his Lord.
Allaah knows best.