Biggles reply 9 regarding half sisters
Are they half sisters according to dna or common knowledge ? My 2C1R was told she had a different father because of her mother's affair but dna shows she IS descended from her legal father ...it was quite a surprise.
Re pedigree collapse ...my grandparents like many other people met at a wedding
Her cousin married his sister so of course their descendants have a higher match but on thru lines only one way may show and the match appears to be higher than expected .
You won't find the other line unless you add all your granparents cousins
This could be scenario for OP
& for many people in small communities
Especially as future weddings in these families other in laws will meet
My favourite Scottish Old maid song
Starts
Och I've often heard it said by my mother & my father
That the going to the wedding is the making of another
I've anglicised the words ...maybe someone can find the original.