I have a combination lock on the side door. Love it.
Usually when I lock myself out it is due to walking out without my car keys and locking the door. I know pretty darn quick I have locked myself out since I can’t drive anywhere. We keep a key in a cupboard in our garage. Where we have a problem is if one of our kids uses the extra key to let themselves in but forgets to put it back. Our house is well built and you can’t break in. Sometimes I get lucky and one of my patio doors is unlocked. If I’m truly stuck I hope I have my phone and can call my H at work to come home and let me in.
Our garage is separate from the house and we don’t lock the door. Our garage is inside our gated property so it is not on the street. We have a coded gate and it would be impossible for someone to drive inside the gate unless they had the code. Someone could walk in if they found the people gate.
For many years we never locked our house. I would also leave my keys in my car. My sister joked she knew I was out of town if she came by my house and the door was locked. Times have changed or I’ve gotten smarter and I lock my door when I leave and even when I’m home.
I have keys for my sister, S and D at my house. They could call me if they were locked out.
No joke - my husband has a chip in his hand that unlocks our front door. I refuse and go with a normal key. I also refused to inject the RFID chip into his hand so he had someone at work do it. (Argh, now anyone reading this who knows us knows exactly who I am!)
I would store your spare key outside your brothers house. If it is found by a thief, it would not work to get into your brothers house and I doubt they would know enough to try your house down the street. This would be very safe. much safer than storing the key on your property. the link from the key to the property it is stored on is too strong. Best to avoid this.
Good luck.
@LBowie - holy JP Morgan!!! Sure the tech has been tested on cats… but holy smokes 
To get our hidden key, someone will need to locate the hidden screwdriver first.
We gave our neighbor across the street the key to our house. At one point we also had one at my parents’ home but they started getting confused about why it didn’t open their door so we took it back. The neighbor has always been home on the many, many occasions we gave locked ourselves out.
@BunsenBurner he bought the kit online at a place called Dangerous Things!
Even holier JP Morgan!!! Eeek.
Neighbor across the street,
neighbor kitty-corner from us,
neighbor, three houses down.
Planter pot, under the pot with tape on underside.
Porch light box, taped with black/grey duct tape behind the fixture.
Taped inside the dryer vent to the outside.
We love duct tape!
We used to keep the spare key in the shed which had a combination lock. However. the new shed has a key lock and the key is kept inside the house.
Not as important now that the kids aren’t living here, but thanks for the reminder to do something like buy a fake rock to get a spare key out into the world.
We just have a key with a neighbor, but it’s true they aren’t always there. I love the idea of hiding our key in their yard. They are a few houses away so I think we’d be pretty safe.
We used to keep a key to my folks house (1/3 mile away) in our car because sometimes we drive them and they don’t have their key with them. H’s car was burgled and they stole they key – to my folks house but it had no address on it and doesn’t work for our house. After that, we stopped storing any keys or valuables in the cars. 
My folks are always surprised we aren’t carrying their house key around with us.
We are fortunate our neighbors are nearly always home. They have keys to many neighbors homes.
The second part to “where to hide the spare key” is “how to remember to put the spare key back” - which we had a problem with a couple of times when the kids were teens - they’d take the key but forget to put it back!
We have a-keypad for the garage and then we put the key in the outside frig in the garage. Trust me it has been used quite a number of times.
Someone suggested keeping the spare in the car console, but if your car is ever stolen and your registration includes your home address, that would be a problem.
We replaced our front door a few months ago and took the opportunity to install a battery powered combination lock. I love it! We use the same combination for it as we use for the garage door keypad, so no one’s memory is unduly burdened. My car has keyless entry/keyless ignition (I keep the fob tucked away in an inside pocket of my purse), so I haven’t had to remember a key or even touch one in ages.
“Someone suggested keeping the spare in the car console, but if your car is ever stolen and your registration includes your home address, that would be a problem.”
For this same reason, I never keep my garage door opener in the car when I leave it on the P&R or in sketchy locations. And we never program our home address into the car’s GPS.
Ours is hidden inside our bbq grill on our back patio.
I’m glad we all of cc alias names!
I keep a spare for my office under a conspicuous rock outside the back entrance. I guess if someone finds it, I don’t worry because you have to enter the alarm code.
I have a keypad for the garage door, and I keep a house key hidden in the garage fridge/freezer under a frozen pizza.
I would feel sort of violated if someone broke into my house…but really…there is nothing valuable here.
Three neighbors have keys. Worse comes to worse…I wait for DH to get home…or he waits for me. We both have garage door openers…and keys.