Who has a key to your home, in case of emergency? Do you have a key to anyones elses home?

My mom recently fell, and the EMT’s had to break the door in. This freaked my brother in law out, and he came by my job today and gave me a key to my mom’s house and a key to his and sis’s house, and asked if he could make a copy of my key.

I allowed him to, as my days of having anything to hide are long over. But it got me to wondering if this was a common thing – to have keys to family members homes? Or are we just nuts?