Mystery cousins

[Phoenix]

I have a group of over 30 US cousins who share DNA with me and with each other. Unfortunately, it is unique to me, and none appear to share any with my aunt, cousin or sib's child.

If one of this number has no English DNA, is it reasonable to assume the link is my non- English DNA?

[kiterunner]

Not necessarily, because it could be that they have a tiny bit of English DNA which doesn't show up in their ethnicity estimate.

[Phoenix]

Have checked, and all the 30 close cousins have Irish/Scottish DNA.

Of course, none have Riley as a surname, my only ancestor who is suggested to be Irish.

I have always written off Irish as too difficult. My ancestors probably left the Island of Ireland c 1750. Finding links (presumably) with potato famine emigrants feels like a thankless task.

Any ideas? (It would, of course, be too simplistic for these mystery cousins to all be from the same close family. All I can say so far is that some appear to have links with the Carolinas.)

[Phoenix]

Not necessarily, because it could be that they have a tiny bit of English DNA which doesn't show up in their ethnicity estimate.

Thanks, Kite!;(

[kiterunner]

I have figured out common Irish ancestors of some of my groups of DNA matches but not managed to connect them up to my Irish line yet.

[Kit]

Ireland seems hard to research to me but it doesn't help that there are no parish registers for about 50 years for the parish I need.