1.5 yr old, has 3 older siblings. peeing everywhere fr what vet said to prove it is his house too?!? Treatment: Lock him in crate all day or meds. Anyone heard of this syndrome? If so -- any suggestions to stop him proving to the other dogs and peeing in our house?
If he is not neutered, it will only get worse. At his age, neutering may not help. You are going to have to be vigilant and keep up with him and stop him. Are you sure the others are not marking too? Some can be very sneaky about it.