What does 'living together' mean according to the law?

Questioner

What is 'cohabitation' according to the law? I am asking this because I am divorced, receive spousal support and have a new boyfriend who regularly visits me. My boyfriend has his own house and is not registered at my address. My ex wants to reduce my alimony. I have had full care of our 3 children for the past 5 years and now because they still live in the house. Two are now over 18 years old.

Lawyer

There must be a joint household with mutual duty of care. Registration is not decisive.

Questioner

Thank you very much for your response!