Hello,
1) As you mentioned you have an inheritance from your deceased mother which remains without being partitioned or distributed proportionate to your shares owing to lack of consensus among heirs.
2) As your mother died intestate the property will devolve among you siblings.
3) It would be pertinent to know for what purpose you need to submit the affidavit of having no ownership.I hope it has nothing to do with determining the partition of the suit in question.
4) Technically until you have in fact inherited the Proprty in the true sense of the term by division of it in metes and bounds or by a family settlement deed you can be treated as an incumbent owner. And that being the case you may submit the affidavit until such mutation or transfer of interest in the property occurs.
5) However since the passing away of your mother you are the legal owner of your share in the property albeit you have not staked claim on it as law confers the right to own your share.
6) In my opinion you can submit the affidavit at this stage.