This is something that troubles me too. My partner and I have been together for 20 years, married for 14 and have 2 children. I love my them, but I'm not sure I'm in love with them any more.
As the years have progressed, it's become more apparent that we have increasingly little in common. We don't really argue, but we don't really talk either. Our conversation pretty much centres around our children.
My partner doesn't have hobbies or circles of friends, they seem content to carry on in a job that stresses them, and then coming home to veg out. We're sort of politically aligned, but they have no interest in politics so we don't discuss it, we don't share the same film, music or books interests.
I like to be active and regularly volunteer with local groups, and am an activist around certain causes. My partner works most weekends, so we rarely spend time together and it's just me and the children.
I'm not deeply unhappy, but I wonder what it would be like to be with someone I really loved and who showed they loved me. Someone with shared passions and interests.