Include content in my PhD thesis from my paper whose content previously appeared in the PhD thesis of one of the coauthors of the aforementioned paper I would want to include content in my PhD thesis from one of my research papers. I am a coauthor of the research paper. The order of the names of the authors in the research paper is not based on the importance of the individual contributions, but it is alphabetical. The point is that the content of the research paper is in turn based on the content of the PhD thesis of another coauthor of the research paper.
Given this situation, I want to know to which extent I would be guilty of plagiarism if I include the content in my PhD thesis with references to both the research paper and the PhD thesis of the other coauthor.
Just be honest: Be clear who contributed what. (And follow institutional guidelines.)