Praise be to Allah.
Fair treatment between males and females means treating them fairly as enjoined by Allaah in the verse (interpretation of the meaning): “Allaah commands you as regards your children’s (inheritance): to the male, a portion equal to that of two females” [al-Nisa’ 4:11]. So if you give the male two riyals, give the female one. But fairness in spending means giving each one what he needs. A female may need clothes worth two hundred riyals whilst the male needs a hat worth ten riyals. Whatever the case, give him what he needs and give her what she needs, such as if one of them needs to get married, then arrange his marriage and do not give the others something of equal value, except those who have reached the age of marriage – arrange their marriages too. This is the issue of spending and maintenance. Fairness in this case means giving each one what he needs.
As for giving voluntary gifts, fairness means giving the male twice what you give to the female, as stated above, as Allaah has decreed their shares in inheritance to be.
As for the one who works with his father in trade or in agriculture, if he gives that voluntarily and seeks his reward with Allaah, then reward in the Hereafter is good. But if he says: I want a share in this world like my brothers, each one of them works for himself and invests his money, then his father should give him this, either as a monthly salary or as a share of the proceeds. But he should treat him like a non-relative, if someone like him would be given a salary of one thousand riyals, then he should give him one thousand riyals per month, and if he would be given one-third of the profits or of the harvest, then he should give him one-third, and so on. End quote.