All quiet on the home front

There has been a slight hiatus in my (virtual) ranting of late because I have been on holiday. On a magical, fabulous vacanza no less, me and the boy and other boy along with two parents, one brother, two friends and assorted Italian in-laws. We were staying on the shore of a lesser known Great Lake (Orta, but don't tell anyone, we'd prefer to keep it lesser known!) and enjoying some wonderful sunshine, food and even, at moments, relaxation.

Kin selection and horizontal gene transfer

Microbiology / kin selection peeps, I need your help understanding something.

Here is a sentence I came across in a paper from the Sterelny/Joyce/Calcott/Fraser collection on Cooperation and its Evolution;

"According to Hamilton's rule, any modification of focal relatedness of genes specifying cooperative behaviors may have an effect on the stability of cooperative behaviors between interacting individuals." (Riboli-Sasco, Taddei and Brown 2013, 281).

I realise the many perils of basing a discussion on a single amputated sentence, but I think it is fair to represent the point being made as the following;