1. Is it Fard on a person to help his brothers financially even though he is in heavy debt himself?
2. Should a person give sacrifice for his parents on 'Eed Al-'Adha even though they can afford it?
3. A woman's obedience is to her husband and not the in-laws. Can the in-laws tell their son to make his wife do every thing they want her to do (Technically she would be obeying her husband). I shall be grateful to you for answering these questions.

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. We ask Allaah to exalt his mention as well as that of his family and all his companions.

If giving (supererogatory) charity prevents one from paying his loans, or if one has an amount that is only sufficient to settle his debts or part of them, then he is not allowed to give it in charity.  Giving charity is a supererogatory act while paying debts is compulsory so the priority is given to what is compulsory over what is not.

On the other hand, some scholars are of the opinion that one may spend in charity since he is not Islamicly prevented from doing so as a general rule.

Therefore, it is evident that helping people is not compulsory for the one who does not have extra money after fulfilling his obligations.

Sacrifice is a confirmed Sunnah.  So, it is not mandatory upon a Muslim to offer sacrifice for himself, or those who are under his responsibility such as his wife, children and parents if they are poor.  Offering Sacrifice on behalf of parents is a praiseworthy act and it is an act of being kind towards one's parents.  Allaah says (interpretation of meaning): {"…And that you be dutiful to your parents….}[17:23].

The act of being kind and lenient to one's parents applies whether they are poor or rich.  However, offering sacrifice on behalf of parents is not compulsory.

The wife's obedience to her husband is obligatory.  If he orders something lawful concerning his family members while she is able to do so then she has to listen to him since it makes her dearer to her husband.  However, a husband should regard the feelings of his wife and should not ask her to do what could overburden her.  If he does so, it may lead to hatred and disagreement between his family and his wife.

Allaah knows best.