I don't agree with this at all. If person A and person B are first cousins, they share one set of grandparents, whether the sibling parents are male or female. Consequently, the genetic contributions of the grandparents is going to be the same regardless of the "type of cousin-ness."
Consider there are certain traits passed on from mother to daughter via mitochondrial inheritance. If Female1 (with mitochondrial DNA A) (F1a) and Male1 (with mitochondrial DNA B) (M1b) have three children, two girls and one boy, all of the children will have mitochondrial DNA A: in other words F2a, F3a, and M2a.
If F2a and F3a have children with non-related males, who have mitochondrial DNA y and z, respectively, (M3y and M4z) their children will still have mitochondrial DNA A.
If M2a, the one brother of F2a and F3a, has children with a non-related female, with mitochondrial DNA X, M2a’s children will have X mitochondrial DNA and not A.
Further consider that if 1st, 2nd, 3rd, or 4th cousins, etc., who all have mitochondrial DNA A, and a history of a trait being passed via mitochondrial inheritance, get married and have children, the children will get a double dose, so to speak of the trait.
I’m not sure, but I think mutation would lessen the trait as the generations progressed though.
That written, mitochondrial inheritance wouldn’t exclusively relate to orthocousins though. Nevertheless, one would think that there should be a term for mitochondrially related cousins.
