The little box has been clean since Sunday night. I don't believe he has peed in the house. He has a certain space he pees which is covered with towels. Hardt o tell if the pee on there is new or old he also hasn't pooped since Sunday either. His biological brother died 2 years ago today of renal failure at age 5. I don't c any of those symptoms in him.

GET him to the vet. If he has a blocked urinary passage, it is fatal if not treated.

Take him to the vet IMMEDIATELY! My cat died from this and he didn't present any symptoms either until he was screaming in pain and had to be put down. This is fatal if not treated and it is extremely painful for the cat!