I have been told my situation is unsolvable using current genetic testing methods from one genealogically-based DNA testing service. My situation is this- I want to test two sisters are VERY likely to share the same mother. But the father of "sister A" is the son to the father of "sister B". This means that a father and son both copulated with the same mother, as strange/wrong/gross as it is. According to that site's representatives, THEIR current testing abilities wouldn't be able to distinquish a genetic difference between the siblings, because their patronymic lines are too close to eachother. Their test would come back saying they are "full" sisters, when in reality they are most likely less than "full", but more than "half" sisters.

I guess what I am asking, is this. Are there any DNA sites/places/clinics that offer custom DNA testing for your average Joe? Money is not so much an issue as is the ability for the DNA tester to adjust their tests to test for a strange situation like my own.

Thanks for the help, everyone.