How come I have dysuria, but nobody else in the family has it?

DYSURIA. Dysuria is common in urinary tract infections or sexual transm diseases, so it is not inheritate. Dysuria is an abormal sensation of burning when urine passes the urinary tract.
Dysuria not familial. Dysuria is usually due to cystitis which is caused by bacteria reaching bladder via urethra. Bacteria, probably e. Coli, come from GI tract and initially were around the urethral opening. Then bacteria reached bladder during "back wash) which occurs at the end of voiding which can suck up bacteria or vaginal urine if present. Thus not by droplet spread in the air like colds or flu, hence only you.
Possible UTI. Dysuria is pain when you empty your bladder. It is a common symptom of a urinary tract infection (uti - or bladder infection). If you have the uti, you will have the symptoms.