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.
The Prophet had many sources of income; for instance, he used to sell and trade and some of his companions used to gift him, and he used to accept gifts but not charity. This is in addition to his share in the war booty that Allaah made for him.
As regards the excellence of spending on one’s family [wife and children], Abu Hurayrah narrated that the Prophet said: "Of the Dinar you spend as a contribution in Allah's path, or to set a slave free, or as a charity given to a needy, or to support your family, the Dinar yielding the greatest reward is that which you spent on your family." [Muslim] For more benefit, please refer to Fatwa 97191.
Subsequently, if your brother is as you mentioned in the question then he is wrong in claiming that he does not need to earn money and that he neglects endeavouring to earn his living out of relying on the Divine Decree. It is known that Allaah linked between the cause and effect, hence, it is for this reason that Allaah urged us to earn our living; Allaah Says (what means): {It is He who made the earth tame for you, so walk among its slopes and eat of His provision and to Him is the resurrection.}[Quran 67:15]
Furthermore, the Prophet clarified the excellence of earning one’s living as he said: "The best food ever that a person eats is that which he earns by (working with) his hands, and the Prophet, Daawood (David) used to eat from what he earned with his hands ." [Al-Bukhari]
Moreover, the scholars stated that a person who is able to earn his living is obliged to do so in order to suffice himself and the people on whom he is obliged to spend, and a person who neglects this obligation (of earning a sufficient livelihood) is sinful.
As regards a person who has what suffices him and the people on whom he is obliged to spend, then he is not sinful for not earning, but it is desirable for him to earn (a living) and some scholars considered this better than devoting oneself for the purpose of performing voluntary acts of worship whose benefit is exclusive to the one who performs them, but they preferred over such an earning those acts of worship whose benefits exceed one’s own self to others, like acquiring knowledge and giving Da’wah (calling people to Allaah). The evidence about this is that At-Tirmithi reported that “There were two brothers (who lived) at the time of the Prophet one used to come to the Prophet while the other used to seek his sustenance (by working), so the one who used to seek his sustenance complained to the Prophet about his brother, then the Prophet told him: “It might be that you are provided your sustenance because of him.”
On the other hand, it is a great mistake and it is a form of cutting ties with kinship that not earning his living saddens his parents, and we do not know which religion makes a child not speaking to his mother and not looking at her, as this is contradicting the religion of Islam, and a person who does this is very sinful.
For more benefit on being kind and dutiful to the parents, please refer to Fataawa 82254 and 87019.
Therefore, we advise you to admonish your brother in a soft and gentle manner and appoint some scholars and righteous people to clarify the truth to him, as he wanted to do good but he did not follow the correct path. You may also show him this Fatwa.
Allaah Knows best.