I thought most people were advocating averaging out the "group" tenure. So in that system, the question would actually be... are
you happy to halve your tenure ((25+1)/2=13) to allow him to link to you?
If it's important to you that you sit together then you would surely consider it and be prepared to drop down the list. Otherwise the only person who's gaining is him. It's not perfect but it at least provides a more palatable option for those with long tenures currently sitting with those with lesser tenure
.
The way I see it, that mitigates the impact, particularly for those with sons/daughters with shorter STH tenure whilst limiting the opportunity for gaming the system, as for somebody to gain somebody else has to make a sacrifice.
Unless I'm missing something