distribution of the shares

If will specifies no. of quantities to be distributed then do accordingly or if you 3 among yourself have any adjustment then make a contract of understanding and from company get the share certificate of particular quantity transferred in all 3s name.

At the time of selling no. of quantities held by each will be considered

You need to inform in the company for splitting of shares against which they will ask you documents such as share certificates, legal heir prrofs, ID proof, will etc.