Tax on sharing of rent by heirs as per WILL DEED

My father left a WILL DEED, wherein he beaquthed a property to my mother only as beneficiary, while specifically mentioned that the rental income be shared by all hiers (i.e my mother, two sisters and my self) equally.

My mother has let out the building to a government office and executed a 11 month rental agreement. The tenent is issuing a single cheque on my mother's name after deducting tax i.e TDS @ 10%.

1. Based on clause in WILL DEED can the tenant be asked to issue separate rent cheque to all the four heirs for respective 1/4th share?
2. Is it necessary that all the four heirs should sign the rental agreement ?
3. Rental income is 18000/- per month. So if four cheques are issued TDS can be avoided also tax return becomes easy. Can I do like this ?