My female ‘half sibling?’ and I, also female, share 2,129 cM.

We DO NOT share the same father. DNA testing revealed that conclusively.

Ancestry puts us into Close Family/1st Cousin. DNA painter includes a 17.8% possible Full Sibling.

We know that’s not possible.

Pre DNA results, a consanguineous hypothesis was considered. enter image description here Could my ‘half’ sibling, be the child of a consanguineous union, between our mother and her father, my grandfather?

As a side note. My sibling has a Single Transverse Palmar Crease.

  • If someone's parents were closely related to each other, there are two things you would see in that person's DNA matches: 1) A lack of matches to an "other side" of the family. That is, all close matches will be determined to be related, say to the known mother. and, 2) That person's matches will systematically show a higher cM count than you would expect from the maternal relationship alone. (I'm assuming that you are sure of the mother, and uncertain of the father.) The cM count of a match to a (1/2?) sibling is not the best test for this because the relationship is already so close. – Jamie Cox Apr 7 '20 at 23:59
  • I haven’t shared here, why a consanguineous theory, was hypothesised , prior to DNA results. However, I am more than a little perplexed, as to the statistics, that a single transverse palmar crease ,is only present in 1.5% of the general population. As opposed to a symptom, which is associated with genetic chromosomal abnormalities. 1.5%!!... I concede that 1.5% globally is an incredible amount of people., but aside from my semi sibling, NO ONE else has this feature within our family. – Curiosity Jones Apr 8 '20 at 22:44

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