Transiting through IST with 2 PNRs. One is OZ, the other is TK. What are the experiences of people nowadays with interlining baggage in *A?

Incoming flight is OZ-TK connection, outgoing flight is TK-TK (OZ codeshare but TK metal). My guess is I have better chance of TK checking through baggage on TK metal but seems a lot of airlines are now in a race to the bottom of doing the absolute minimum and are now saying "no commitments" for separate PNRs.

Anyway, have prepared for the worst case which is to clear immigration and check in again at IST if they don't allow baggage check through. I am traveling with family (4 people in the same PNRs). Is it allowed in IST to just have one person clear immigration and recheck baggage, and the rest of the family remain airside? Also saves visa fees. Also possible in other airports to have airport staff do the baggage transfer at times, but probably not with TK in IST?