Is it permissible to secretly take money from one's brother if this money is originally the share of the questioner and her sisters from their parents' pension and the inheritance from the sale of land, and the brother has evaded giving it to them, in addition to the price of the sacrificial animal (udhiyah) that the questioner paid to him in advance?

If the pension is a grant from the state or another entity, and the granting authority designated it specifically for you and your sister, then the remaining heirs have no right to it. Your brother must return what he took from it without permission. As for disputes, they should be referred to the Sharia courts. Regarding your brother's seizure of your share of the land's price and his refusal to pay it, you are permitted to take your right from his money when you are able to do so without his knowledge, and the same applies to your sister. This is known as the issue of "seizing one's right." However, it is not permissible to take the money you gave him to buy a sacrifice without his knowledge, unless he denies it and refuses to return it.