Forget cross cousins, marriage even to maternal uncles was allowed.
If you know Gupta dynasty, one of the sons of Chandragupta II(Vikramaditya) named Ghatotkach Gupta, married Munda who the daughter of his sister Prabhavati Gupta.
But then marriage in same Gotra wasn't permissible and children of two brothers were considered siblings
Like Arjun Dusshala, Kansa Devki
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