in the share certifcate flat is standing in name of both the brothers Atul R Mehta & (2) Akshay R Mehta.

2) if flat is standing in joint names society should issue maintenance bill in joint names

3) there is no such law that maintenance bill has to be in name of one member only

4) the person whose name stands joint second or third in the share certificate can become an associate member (Sec 2(19)(b) of MCS Act

5) If the flat is held by a single member, no person can be admitted as an Associate member unless his name is entered in the share certificate after execution of a gift/ sale deed and payment of stamp duty and registration charges.

6) issue legal notice to society to raise maintenance bill in joint names

If the property belonged to yor deceased father and you are the only legal heirs to your deceased father, then you may both apply for transfer of shares to your names, jointly.

You can comply with the necessary formalities in this regard.

Even after fulfilling all the conditions meant for this situation, if the society is refusing to include both the names, you may take legal action as per law on further issues.