Is it mandatory that shared first/co-first authors (1) have equal number of CRediT roles reported and (2) are alphabetically-arranged? [biomedicine]

We’re probably making a mountain out of a molehill here, but I am posting here in case my group is missing some insight.

I’m reading the ICMJE recommendations (https://www.icmje.org/recommendations/) and I can’t find direct advice on these issues. By “equal number of CRediT roles reported”, I mean the same number of disclosed roles following CRediT (https://credit.niso.org/).

Can journals ever impose their own or disagree with the authors’ authorship sequence decisions?

We are submitting a manuscript of a basic science research wherein two people – say R1 and R2 – substantially contributed to the endeavor compared to the rest of the authors (nevertheless, everyone satisfied the four-point ICMJE authorship criteria).

We have amicably and unanimously decided that R1 and R2 truly deserve being co-first authors, even if the number of the CRediT roles they fulfilled are different (as an hypothetical example, while R1 was involved in conceptualization, methodology, investigation and formal analysis and R2 was involved only in conceptualization, methodology and formal analysis, R2 undoubtedly led the whole team in methodology development and formal analysis step). Furthermore, R1 personally believes that while her name is “alphabetically first”, she wholeheartedly wishes to give some spotlight to R2 (so the paper can be in text-cited in the future as [R2 et al., 2026]) as R2 has fewer papers and that, at the end of the day, the publication will indicate in the report that they contributed equally anyway.

Are there publication and/or ethics issues we should consider with these decisions?