Family property distribution

FACTS & DETAILS My Grandfather had three sons (Rajjan Singh, Haripal Singh & Mahipal Singh) Rajjan Singh got married with Our Mother (Rajbiri Devi). When Mother had got one son Omvir Singh, Father Rajjan Singh had died. Due to very young age of Mother – Society arranged and Mother re-married with Haripal Singh. Mahipal Singh not got married and died at about 40 years of his age due to sickness. Now Father Haripal Singh got three sons – Satyavir, Dharamvir & Santosh. Putting all together – four brothers – Omvir, Satyavir, Dharamvir & Santosh (from two fathers & one mother) Now, The Grandfather got 60 bigha land. The distribution of the land according to the society – 30 Bigha to Ombir and 30 Bigha (10 Bigha each to Satyavir, Dharamvir & Santosh). Since, from birth, all brothers living like brothers and having one mother only then why one brother got entitled complete half portion of all properties. Query – Is there any legal way that all brothers can get equal share from all the parental properties ?