Wow! Your in-laws sound like people that don't understand or respect boundaries at all. Honestly, that would send me off the deep end, so I commend you for your patience, but it's time for them to learn a few new things! Grrrr.... I absolutely agree with the idea of locking all doors and you can say that it's to prevent theft, etc., but do you have a fenced yard with a gate? If so, I'd put a padlock on the gate and tell them that it's there to keep people from letting Zeus out by mistake,to keep people from coming in and surprising Zeus b/c he might bite them and maybe you can point out that it's safer for your children to play in a locked yard, too. We have padlocks on our gates to protect our dogs. Our family isn't near by, but our neighbor's 4 y/o granddaughter opened our gate and walked right in one day to pet the "pretty doggies". Agh, that was just too close for comfort for me. She could have let the dogs out or they might have knocked her down in their excitement. I don't *think* that mine would've bitten her, but they are dogs and they do have teeth, so anything is possible. Our padlocks went on the same day! I'm all for locks on fence gates. Not only can you help protect Zeus this way, you might just get some well deserved privacy, too.