Literally here for opinions.
My DS is 17 & has always spent his time 50/50 with his Dad & me - for the last 14 ish years.
His relationship with his Dad is a bit strained at the moment & something that has caused a few issues recently is that he doesn’t have his own key to his Dad’s house.
AIBU to expect a 17 yr old who lives at your house 50% of the time to have a key?