My 7 month old yorkie keeps on marking on our bed. Generally he is not allowed in the bedroom as our other 14.5 year old yorkie sleeps in there most of the day,but given chance he will go in and do this on our bed.He has also done it on his own bed in the kitchen.He has been perfectly clean for 2 months now, i just wondered if you new the reason for this new behaviour. Should i consider having him castrated,would this help?