Technically they can Gita as according to religion, they actually can get married as marriage between first cousins onwards ( by blood) is allowed in Islam and in this context even Haidar and Zoya can get married, had they themselves not considered their relationship as that of siblings.
In fact, i think in the oldern days getting married to cousins was practiced often because close knit families wanted to protect their children and keep their wealth within the family etc and thus made their children marry cousins whom they know well.
But these days people avoid getting married to such close ones by blood because consanguineous marriages leads to getting babies with inherited disorders etc..
So although, AsYa and AyRa can get married, them being cousins will be too much. each and everyone will be really related then and this will become a real family saga then with Badi Bi at the top most.😆