Polyandry from Ancient Greek πολύ (polú) 'many' and ἀνήρ (anḗr) 'man') is a form of polygamy in which a woman takes two or more husbands at the same time
The problem with that though is that it could be difficult to know who the father of the child is...
That's not a problem, if the cultural belief is that they
all are.
It would be a problem for you, and for those who share your cutural norms; But why would it be a problem for those who practice it?
It takes a village to raise a child. If all (or many of) the men in the village agree that they are all the child's fathers, so much the better.
Wherein lies the "problem"?