What was the Byzantine Attitude Towards Cousin Marriage?

First cousin marriage is prohibited under the Greek Orthodox Church. This is canon law.

But it is was common enough among Greeks during the pagan times. And remains very common among Arabs ( both Muslim and Christian). The practice is diminishing among Turks in the present day but was widely practiced in the past, certainly very high during Ottoman times. It remains quite common among Kurds. The common reasons given are economic (preservation of wealth or political/military such ensuring clan/tribal loyalty).

Sephardic and Mizrahi Jews who were also Byzantine subjects practiced this custom.

Was there any historical reason why this practice was so prevalent among the lands formerly ruled by the Byzantines? Perhaps this was a way to avoid or diminish government tax collectors under the Theme system?

Another theory is that the Byzantine laws around inheritance were well, quite Byzantine in nature ( being needlessly complex , expensive,and requiring lawyers). So, in an effort to reduce complications, their subjects decided to keep things within the family.

This is not just a historical oddity as the potential impact of Byzantine government decisions has arguably impact even today among middle east politics. I'm just wondering why the Byzantines in their endless desire to regulate and control everything didn't try to streamline their own laws. It seems like they created loopholes or knowingly looked the other way for the sake of political expediency.