Family Jewels Meaning

(idiomatic, euphemistic) Testicles.

Example: Used other than as an idiom: see family,‎ jewels.
  The whole crowd cringed as he got hit right in the family jewels.
1971, R. Z. Sheppard, "Three's a Crowd," Time, 5 Jul.,
  But what do three testicles mean? A mystical trinity illuminating some absurd need to procreate? A symbol suggesting a metaphysic of pawnbroking? Likely as not, it is simply an animation of the familiar euphemism, "the family jewels."