First off, citing papers is not about giving credit to first authors, it is about making literature traceable to readers. This is a key part of scientific writing, providing sources. The format for citations is of course focussing on first authors who may, or may not, be the main contributor (remember that author order varies between disciplines). A secondary aspect is the fact that many evaluations of academic status is based on authorship and as such authors may not be credited as much as they should. This is, however, not the reason for why we reference the way we do. So, from this perspective, I do not see why you necessarily need to emphasize the name of someone other than the first or second author (I am now thinking Harvard-style references where two-author papers have both names listed in the in-text reference).
If there is a scientifically based reason for highlighting the originator, one could write
Concepts One and Two (reference to B) were first developed by A [then I would argue some form of explanation of why this distinction is scientifically important should follow or be included]
A originated the concept one and two (Reference to B) [then I would argue some form of explanation of why this distinction is scientifically important should follow or be included]
Note that this would seemingly take away the importance of B, which in many reference systems would look strange and implicate something may not be right with the articles. I therefore think it is wise to clarify why you feel the work of A is such that it requires highlighting. Clearly, I cannot judge the case since all details are unavailable. As a side point, reviewers will likely pick up on any inconsistencies and ask for clarification in a case such as this, unless the reasons for the formatting is either clear from your writing or well known in the community.