Land Access Rights Query

My grandpa had a residential land in the main road with a width 30ft facing the main road and length of 300ft running perpendicular to the main road. The only access to this land is through the main road. During property settlement, my grandpa settled the first 150ft length of land to his elder son and the backside 150ft length of land to his younger son. Starting from the main road and till the end of the plot at the backside, he made total common access of 7ft along the eastern face of the land. After a few years, the younger son able to get an entrance to his backside plot though a secondary access road at the backside, so there is no need of utilising the main road. Now my question is the backside part access area (150ft x 7ft) is for the younger son plot, does the elder son is also having rights in the backside access area even though there is no purpose for him to gain access through it.