The earnings of the children who stay with their father belong to the father. It cannot be counted as a separate asset. At this time the father meets, the expenses and spending are made from the father’s earning. Yet if the children agree to the joint spending, their earnings may be considered in accordance with this agreement.The earnings of the children who stay with their father belong to the father. It cannot be counted as a separate asset. At this time the father meets, the expenses and spending are made from the fathers earning.

Yet if the children agree to the joint spending, their earnings may be considered in accordance with this agreement. I agree that sum certain money of mine is jointly to be spent but sum certain in money belongs to me etc. As long as there is not such a clear agreement, the money of the children belongs to the father whom they stay with not to themselves.

However, the Prophet Muhammad recommended fathers to be fair among their children and be accurate about the rights of the children.
Although there has not been much talk between the father and children about the issue, fathers consider the children effort and give their dues.