Land Sale deed on Grandfather's name

Hi, My friend's father(S1) purchased a land by investing a part of his own money in family property but made sale deed on his father's(P) name 20 years back. P has three sons. S1 is first wife son and S2 and S3 are second wife sons. Land is divided into three equal parts but a portion of S1 share is divided into two parts again stating that borewell installed in S1 belong to S2 & S3 also. But S1 is planning to sale his share and start up a new business. Due to this division his share is not fetching need funds. The S1 share is divided as 80:20. So, S1 asked P to revert the positions so that S1 gets the area where there is no borewell. so that S2 and S3 can use the bore and no partition required as S2 & S3 want to cultivate agriculture they do not want to sale their portions for which P is not accepting. Now my question is can S1 claim his half share as he is first wife son and he also invested his money in purchasing the land. or how can he get the desired area of land so that his share is not divided into parts. Thank you in advance for your valuable suggestions.