You said earlier that keys a minor third apart tend to be "ghost cousins" and while it could be argued that this is solely because that's the distance between a minor key such as D minor and its relative major , F, I was gonna ask do u think that movement between said keys can happen even if they are both major?
when i said that, i was specifically talking about when both keys are major (or both minor). if one is major and the other is the relative minor, i would consider those to be the same key. but indeed the reason that (for example) Fmaj and Dmaj slip so easily, is essentially the same reason that Dmin slips so well to Dmaj. (for the folks at home, you might know this as the "parallel major of the relative minor" of F). but the important thing is, this is not discovered by deliberately trying to slip a minor third. it's just simply by finding how you want the song to go, and go there. Zero times have i ever deliberately decided to do a minor 3rd slip on purpose. in fact, sometimes i am driven to avoid it and find some other amount to slip, just for something new