▁and ▁their ▁children , ▁first ▁c ous ins , ▁and ▁nep he ws / nie ces ▁and ▁their ▁a un ts / un cles ) ▁are ▁prohib ited ▁from ▁marry ing ▁each ▁other , ▁but ▁that ▁church ▁tradition ▁sets ▁no ▁prohib ition ▁against ▁marry ing ▁a ▁more ▁distant ▁relation . ▁However , ▁Gregory ▁used ▁a ▁method ▁of ▁reck oning ▁degrees ▁of ▁kin ship ▁( or ▁cons angu inity ) ▁that ▁was ▁un famil iar ▁to ▁many ▁living ▁in ▁the ▁mid - e ighth ▁century . ▁U bl ▁has ▁shown ▁that ▁Gregory ' s ▁method ▁of ▁reck oning ▁degrees ▁of ▁kin ship ▁was ▁one ▁that ▁would ▁come ▁to ▁be ▁known ▁as ▁the ▁" script ural " ▁or ▁" can on ical " ▁method . ▁Bon if ace , ▁the ▁pap acy , ▁and ▁apparently ▁most ▁of ▁Western ▁Europe ▁ca . ▁ 7 5 0 ▁followed ▁a ▁different ▁method ▁of ▁reck oning , ▁known ▁as ▁the ▁" R oman " ▁method , ▁where by ▁a ▁restriction ▁within ▁the ▁second ▁degree ▁merely ▁pre cluded ▁sib lings ▁from ▁marry ing ▁each ▁other ▁and ▁parents ▁from ▁marry ing ▁their ▁children , ▁and ▁implicitly ▁allowed ▁all ▁un ions ▁beyond ▁these . ▁Thus , ▁Bon if ace ▁( mis inter pre ting ▁Gregory ' s ▁" can on ical " ▁method ▁of ▁meas uring ▁kin ship ▁for ▁a ▁" R oman " ▁one ) ▁took ▁this ▁passage ▁in ▁the ▁Lib ell us ▁to ▁mean ▁that ▁Gregory ▁permitted ▁first ▁c ous ins ▁to ▁marry ▁each ▁other ▁and ▁nep he ws /