I posted about this a year ago, as we have an issue with keys here and it is still not resolved.
We have three teens, two mine, one DH's. Both of my kids have their own door keys to my house and to their fathers. DSS has a key to his mothers flat but not our place.
DH's ex is a nut job and we do not trust her not to use the keys and come into the house.
Occasionally it is a pain that DSS does not have a key, we have cleaner who is here most days when the kids get home from school or I am here. If anything changes DD has to get home to let DSS in. We did look at a key safe with a combination or a remote access thing on the front door, but never went any further.
What do others do?