Stirk, 49, and Harbour, 44, will join the Rogers name as part of the practice's long-awaited succession strategy.
The move confirms long-standing rumours that the pair have been Rogers' anointed successors for quite some time.
Together the pair has 45 years experience with RRP.
It is as yet unclear what order the names will go in but there can be no doubt that Rogers will remain first.
Harbour said this afternoon: 'I feel pride but I'm also slightly terrified - thats only human.'
The duo has also insisted that the route to the very top of the practice is still open to others. There are currently 10 directors - one of whom is Rogers, who will remain an active chairman.
Harbour said: 'This is not a closed shop; other names may well be added in the future.'
Also speaking this afternoon, Stirk said: 'It's our responsibility to find the next generation and not to louse up.
There is a vast amount of knowledge in this office and the idea of that disappearing is just too tragic to contemplate.'
The deal will have to be formally agreed by the board in two weeks.