Can a child have a larger match with someone than a parent?

[Mary from Italy]

My son's results are in, and Thrulines came through quite quickly, which was useful.

However, it threw up something a bit odd: it showed a common ancestor for my son and one of his matches who I don't have.

It's a small match, only 8 cM, but a genuine one with a good paper trail, and as it's on his English side I obviously have the same common ancestor.

I've checked the match out, and she's showing as no match with me.

I realise that the amount of DNA inherited is random, but is it possible for my son to have a larger amount of DNA shared with a match than me?

He can't be related to her through his father, because my OH's tree is 100% Italian.