Siblings have some of the same DNA, but don't actually "share the same ancestral DNA." You don't get exactly 50% from each parent, and on back. So you can have an Indian ancestor from the 1600s, but not a single bit of DNA from that ancestor. Or you can have a larger amount, perhaps enough to have "high cheekbones," which I always thought was irrelevant, as I have relatives with "high cheekbones," but no Indian ancestry all the way back to immigrant ancestors on all lines.
Siblings have some of the same DNA, but don't actually "share the same ancestral DNA." You don't get exactly 50% from each parent, and on back. So you can have an Indian ancestor from the 1600s, but not a single bit of DNA from that ancestor. Or you can have a larger amount, perhaps enough to have "high cheekbones," which I always thought was irrelevant, as I have relatives with "high cheekbones," but no Indian ancestry all the way back to immigrant ancestors on all lines.