Are some people more prone to getting varicocele?

Lacking venous valve. Boys or men who lack venous valves in the spermatic vein or veins between testicle and left renal vein are more prone to developing a varicocele. They are only discovered at approaching puberty or later by presence of a scrotal swelling that feels like a bag of worms when subject is standing up or as part of an infertility workup.
No, .... There has been no known acquired factors to make men prone to develop varicocele, and it's a disorder of congenital venous valve defects of spermatic veins. Don't worry.