Need help with unfriendly cats (long)

I am new to this forum and need some serious help with my cats. We are a family of 5 and have 2 female cats from the same litter that we adopted when they were about 5 months old. We have had them for almost 4 years now. When we first got them we read the books and did all the things to introduce them to our family and house. But they did not make the transition well and have never really bonded with us. They are very skittish and scared and hide 95% of the time. They do not like to be touched or held in anyway and will fight tooth and nail if we attempt to corral them. They have been known to pee outside the box when they are unhappy with us in some way. Over the years we have tried various things to try to get them acclimated to us. We have taken them to the vet only to find nothing wrong except my husband and I suffering from serious cuts and scratches from them clawing us to get away. Nothing has worked and it seems to be getting worse. The final straw was two weekends ago when my teenager had a sleepover. Knowing that they would never go past a group of kids to get to the litter box we corralled them into the room where the boxes are for the night. They have been corralled in this room before. But since the sleepover they have taken to peeing on the kid's beds sometimes when the kids are there even. This is just unacceptable. I am familiar with the process to get them back to peeing in the litter box since we have been through it before. This seems like more than just a peeing issue. We have contemplated meds but if we can't handle them how are we going to pill them. And I am not sure the meds will help with their basic personality. No shelter will take them since they are not adoptable. We are getting tired of constantly "tiptoeing" around the cats so as not to upset them and are running out of ideas. It is hard to want to put a lot of effort into these cats when they are not friendly in any way. But on the other hand it is hard to watch them be miserable too - I am sure that they are not happy in our family. It is as if they just can't get used to the amount of commotion that comes with a family of 5 (2 of which are teens with lots of friends). And I fear it is only going to get worse. If anyone has any suggestions of things we might try we would really appreciate it.