When siblings contribute to a research paper, do they need to declare their relationship in the competing interest form? Siblings contributed to a research paper. The publisher asks to fill no competing interest form. Citing the journal in question, it contains the following check box:

☐ The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to
influence the work reported in this paper.
☐ The authors declare the following financial interests/personal
relationships which may be considered as potential competing
interests:

What the siblings are obliged to declare? Does &quot;personal relationships&quot; requires them to declare their personal relationship? But what if their relationship certainly does not influence the work? Any suggestions on whether to declare their relationship or not?
There is already an assumption that authors working together have some level of positive relationship - whether colleagues, advisor/advisee, or relatives. These things need not be declared, because they don't influence the content of the work besides all the authors standing by it (which is a minimum requirement for even submitting the paper).
If a sibling has a stake in a company selling widgets and the paper is about how widgets are superior to doodads, then this likely should be reported because the paper could be influenced by a sibling's desire to help their relative's business.