Kids profile picture show in parent account

We have family sharing set up for my husband and I and our 2 older kids. When my son changed his profile picture, it changed it on my account. When I changed it back, it changed it on his account. Somehow our accounts are linked. Also, some of his contact names show up in my emails....like he has me labeled as "Mom" in his contact book so when I send/receive an email sometimes it shows up as Mom and not my name. (I think this is only on my end...I hope...but I'm not sure!)

Any idea why this is happening?