Cousin Siblings

[darkerhorse]

If my paternal grandparents were third cousins to each does that mean I'm fifth cousins with my siblings and with myself?

If yes, would siblings share more DNA than expected or does it just mean that what they share is expected but comes from a smaller gene pool than normal?

Same kind of questions with the siblings and their 1st cousins.

[MarcuccioV]

Not necessarily "more" DNA, but certainly from a smaller gene pool. Not certain on the 5th cousin thing, perhaps on paper, at least. I think the sibling relationship might cancel that out.

This is probably a good question for a genetic scientist...

[darkerhorse]

I wouldn't think it cancels it out, rather shouldn't it me cumulative - siblings plus 1st cousins = greater than siblings alone.

In the extreme example, wouldn't children of siblings share more DNA than average?

Wouldn't they be 1st cousins to each other, by definition?

This was likely the early norm in ancient times.

In a similar situation, if three brothers married three sisters wouldn't their children be double first cousins, sharing more DNA than single first cousins?

[darkerhorse]

If my paternal grandparents were third cousins to each does that mean I'm fifth cousins with my siblings and with myself?

If yes, would siblings share more DNA than expected or does it just mean that what they share is expected but comes from a smaller gene pool than normal?

Same kind of questions with the siblings and their 1st cousins.

I forgot they were also third cousins in another way - through grandfather's mother and grandmother's father. So they were double third cousins.

I wonder what that does to the concept of cousin siblings and DNA sharing?