It is possible that the word "feet" here may have been a more respectful way to refer to the genital area of the body. (See: [[rc://en/ta/man/jit/figs-euphemism]])
The meaning of this metaphor is unclear. It was probably a known saying in that culture. Alternate translation: "you are related to me by this blood" or "you are my husband because of blood" (See: [[rc://en/ta/man/jit/figs-metaphor]])