Contacts are automatically saved

Hi

some time before i got iphone 7 plus and now i have iphone 11. I have signed out from my apple id on iphone 7 and make husbands apple id. Now whatever contact my husband is saving in iphone 7 plus they are automaticaly saved to my iphone 11 contact book. When i delete it from my iphone 11 then its automatically deleted from my husbands phone as well. I cant understand the problem please do help me what i should do.

regards

sidra