I have a wife and 2 children. We all lived at the flat from 1998 to 2006 with the children going to school locally. After 2006 they moved to the new house and went to school there.
The flat has 2 bedrooms. My wife and I own both properties. I receive utility bills at both addresses, tv licence at both addresses, council tax at both addresses, my tax returns go to the flat, my wife's P60 went to the flat until 2011, we are both registered to vote at both addresses, my bank statements and credit card bills go to the new house, my wife has bank statements going to both addresses.
I have my mother, brother, nieces, uncles and aunt living minutes away from the flat still. We have friends who live near the flat but we also have new friends who live near the house.
As my wife still works part time near the flat, I would say that we both have social lives equally at both places.
I'm not sure about your 1st question about the family spending time at the flat. After 2006 they moved to the house so they only visited the flat on some weekends and holidays to see other family.