Anyone been through this and found a solution please help.

Got two neutered, fully healthy (vet checked multiple times) female cats, 2.5 years old. Both were from same litter - kittens surviving together on street when we adopted them, one is calico one is orange. They are Peeing all over the house since a year, it's definitely marking and territorial behaviour anytime a stray cat shows up around the house far away and doesn't even bother my cats. One starts peeing and then the other follows. They use litter box only for pooping now, pee in the sink or drainholes in bathrooms or all over the house. I tried different litters, various sprays, feliway, nothing works. They have 3 litter boxes at 3 diff places. Both are happy in the house and super cuddly but everytime after sensing another cat in neighbourhood, the calico starts howling and ready to fight, starts marking. She also gets angry on the orange cat and fights with her, both end up peeing at different places on beds pillows floor, our clothes curtains everywhere even on walls. Whole house has been marked now so many times and we have cleaned with dettol, enzyme cleaners, vinegar and various smell removing sprays nothing works they do it again. Washed all beddings in dettol multiple times. Both cats sometimes fight over each other cuddling too much with my mom, like jealously. They never hurt each other to cause any physical damage no deep scratches ever and they cuddle together often. I'm at my wits end and very depressed we have removed all pillows from the house now and stored them in boxes in a room. They keep peeing every 3-4 days and I feel it's very behavioural and they won't stop. Don't want to give them away and cannot continue with soo much pee everyday it's making me and my parents very upset and insane. Has anyone faced something like this ? Will this ever change or I'm doomed for life with cat pee all over the house and clothes forever? If anyone's found a solution ever please help or guide I will be very grateful😞🙏feels like I will go crazy with this happening endlessly