So, if I have this right, I should be able to grow broccoli rabe and arugula to seed together, without issue. One is "brassica rapa" and the other is "eruca vesicaria." Spinach is a member of the goosefoot family, and unrelated to both. So all three should be ok together.

Squashes on the other hand, they simply should not be mixd, as all have basically the same name in latin.