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.
Ibn Qudaamah mentioned in “Al-Mughni” that there is a consensus among the scholars that the children are obliged to spend on the poor parents who have no earnings. Therefore, if your patents are poor, you are obliged to spend on them. Also, your brothers (and sisters) who are well-off are obliged to spend on them, and the share of each one will be according to his ability, as Allaah Says (what means): {Let a man of wealth spend from his wealth, and he whose provision is restricted, let him spend from what Allaah has given him. Allaah puts no burden on any person beyond what He has given him. Allaah will grant after hardship, ease.}[Quran 65:7] For more benefit, please refer to Fatwa 90246.
As regards spending on your brothers and sisters, according to the most preponderant opinion, it is not an obligation on you unless they are poor and you are an heir to them (in case they die), however, you are not so because you are prevented by your father from inheriting them. However, spending on them is a good deed for which you will be rewarded, Allaah willing. Moreover, spending on a relative is both a charity and an act of keeping ties with kinship; for more benefit, please refer to Fatwa 82987.
Besides, you should know that the right of the parents is great and it cannot be rivaled by the right of the spouse or of any other person. But this does not mean that you should be unjust to your wife or your children; rather, you should give every one his right according to your ability.
If we presume that the right of the wife conflicts with the right of the parents, then the right of the parents comes in priority. Your wife and your children should understand that (i.e. your financial obligation towards your parents) so that they would help you in being kind and dutiful to them.
Besides, you should beware that your wife and your children be a reason for severing ties with your parents, because severing ties with the parents leads to the loss of this worldly life and the Hereafter.
You should always remember the saying of Allaah (which means): {O you who have believed, indeed, among your wives and your children are enemies to you, so beware of them.}[Quran 64:14], and the Saying of Allaah (which means): {And We have enjoined upon man goodness to parents.}[Quran 29:8]
Allaah Knows best.