Will the two Umrahs for my brother and grandfather be accepted, and how will they reach them, and what should be written for them? And is it permissible for me to perform another Umrah in the new Hijri year after performing Umrah in the previous year?

It is permissible for you to perform Umrah on behalf of your grandfather and brother after performing Umrah for yourself. The deceased benefits from the Umrah dedicated to them if it is performed correctly. The knowledge of how the reward reaches the deceased rests with Allah the Almighty.

Ahmad said: "Everything good reaches the deceased, according to the texts mentioned concerning this." Allah may elevate the status of the deceased through the supplication of their child, and charity given on behalf of the deceased benefits them by the reward reaching them. The occupant of the grave benefits in their grave from the rewards presented to them, as the grave is the first stage of the Hereafter. What is important is that the deceased benefits from the reward. As for the question of whether it is Umrah, charity, or light, knowing this does not entail anything. It is permissible to repeat Umrah multiple times in one day or on other days.