DNA Test Advice

[close1]

My Grandmother has done a DNA test with Ancestry and i recently have done a test.

I have two questions.

My Grandmother recently had a match of 25cm and the same match appeared in my results at 21cm.
Is it possible for my result to be that close to that match even though it's two generations different?

My Other question is, My sample through thru lines suggest a Half second cousin through my father's grandfather line, However the shared centimorgans is only 13cm 1 segment.

The details about my Great Grandfather and the other person's tree line up such as dates of birth, marriages and death are correct.

Is that too low to be that relationship?

[aghadowey]

This site will give you the probable relationships based on cMs-
https://dnapainter.com/tools/sharedcmv4

[Pheno]

If you can confirm the suggested dna match with a confirmed paper trail then it is likely to be correct.

Pheno

[Glen in Tinsel Kni]

Its worth bookmarking the site aghadowey has given the link for but in short whilst a h2c at 13cM is at the low end of the scale it is entirely possible. It's almost the most distant relationship that is guaranteed to share DNA. Around 15% of 3rd cousins don't share dna so if a known 3rd cousin takes a test and isn't showing as a match they are in the minority but not unique by any means.