We Cannot Marry Because My Grandmother & His Mother Are From Same kindred

please i need your advice

My fiance and i got engaged last December. he is a truly amazing man and posseses all the good qualities of a husband. he is from Enugu state mgbowo village and im from
Anambra state.

normal family investigations were conducted. it was found that his mother and my maternal grandmother are from the same family/kindred. the basis of our affinity is that we share a common ancestry so the tradition according to the elderly women say that my fiance and I are forbidden to marry, that if we have kids they will die. our alternative is to do a ritual to break our so called blood link.  the elders refuse to listen to us despite the fact that im not from my fiances village and the fact that my mother married outside of mgbowo village

my fiance and i are christians and will not partake in the ritual. iv told my pastor and he said he sees no close link between us that we can go ahead and marry because even in the bible the list of forbidden relationships among family members does not include my fiance and i . my parents advise i end things with him but i believe this man is my God sent husband and we are ready to fight this. if we were close cousins i would understand but our family tie is far. my theory is, if something is forbidden there should be no alternative. i need advice