For the benefit of readers of this post, let's clarify what seems like a redundancy here, namely 'past history', since history implies past events.
Shouldn't it therefore be just 'medical history'?
In medical settings, ' a history of stomach cramps..' refers to the onset of this symptom, which continues to this point in time.
'a past history of stomach cramps...' refers to having had, at some time in the past, the symptom of stomach cramps, and that this condition has resolved, either spontaneously, or by some form of medical intervention, and so has not been in evidence for some time.
A native speaking medico would say:
Other past medical and family history is/was unremarkable.
Here, the verb agrees with the singular 'history'; and 'other' indicates that some piece of the history has been referred to that may have relevance to the current symptomatology, but that the remainder of the history - the 'other' - is unremarkable.
'medical' and 'family' are lumped together as adjectives qualifying 'history' -
Student or Learner