Payment to NRI in Either or Survivor account

I have purchased a flat for 86 lacs.....there were two sellers son(NRI) and mother(Resident Indian).....I have paid them equally i.e. 43 lacs each

I have deducted the tds differently for both the sellers as per their residential status. For Son(NRI) I deducted tds as 20.8% on 43 lacs and for mother I deducted 1% on 43 lacs.

But I have made payment to them using self funding and home loan... in sellers either or survivor account (where mother is primary account holder)......using separate cheques in mother and son name.

So my question is, can I make payment to NRI in their either or survivor saving account where his mother is primary account holder or NRO account is mandatory. I have deducted his tds as per NRI status.