How to suppress my grandpa's ridiculously high sex drive?

Before you hire another caregiver think very carefully about the qualities that caregiver needs. She should be older and very experienced in home care. A good solid woman and I mean that literally, who will not be intimidated by grandpa's actions and have your family's full support for whatever actions she deems necessary in certain circumstances. This can only apply while they are in the house and not when he is out alone in public. Whatever he does then or how he spends his money are of no concern. If he is misbehaving he must bear the consequences. in the house the caregiver sets the rules for gpa with dad's prior approval and bad behavior has consequences such as having his allowance with held for that day at least. everytime he wakes the caregiver at night he looses a days allowance with no exception. As with a child threats must be followed by actions. It is very clear that he will do anything he can to get rid of any caregivers. He wants to live in pig heaven. If he becomes violent as in destroying things in the house or threatening the caregiver the police should be called imediately and he will be taken for a psychiatric evaluation.
Pam's idea of the wooden spoon to the penis is tempting but could get the caregiver in a lot of trouble. The best thing is to totally ignore it and tell him to put it away. If he does not then leave the room and do not provide any further service till he behaves or call the police and file a complant. Do not yell or argue just warn him of the consequences and follow through. caregivers have to be prepared to deal with this kind of situation and if the family does not provide support they are with the wrong client.
Bamboo I realize you are worried about your parents but you are not responsible for grandpa they are. It may be hazardous to their marriage to continue in this way but your mother is complaining to the wrong person. she needs to sit down with her husband and the two of them figure out the reason he chooses not to come home when he is in town. If you have a live in caregiver let her do the job she is paid for. Dad does not need to be babysiting. it sounds to me that there is more going on here than Gpa's inappropriate sexual behaviour. This really is not your problem. You are a young wife and your attention should be on supporting your hubby while he finishes his education and takes those all important final exams. it is a very stressful time for him he does not need this diversion. Been there done that I married a medical student.

Does your grandfather have dementia? There may be a medical reason for his sex drive or on the other hand he's really lucky to be able to be sexually active at his age. When was he last to see his doctor? Someone needs to go with him to explain the concerns. Is grandpa competent to make decisions on his own? Hiring male caregivers would be a good option.

Just another thought . Have grandpa's testosterone level checked and you may find an Estrogen product will slow his urges

Is he on any meds? I've learned that certain meds (I believe meds for Parkinson's - don't quote me) can increase sex drive in males.

I heard they put saltpeter in food at jails a long time ago. Maybe the dr could give him something to take away the urges?

Tempa, LOL I haven't heard that one in years. Saltpeter is a vasodilator, and years ago was used for angina pains. The side effect was ED, you are right. But it was probably used in jails as a food preservative (bacon, corned beef, jerky and hot dogs).
The treatment today for grandpa is female hormones, or possibly saw palmetto. Saw palmetto is estrogenic and should not be taken by women.