What I have been thinking regarding my lack of attachment with my mother may have to do with a long hospital stay directly after birth, thus missing a crucial attachment period. If my childhood friend's moms were my mom it's hard to say whether I'd be attached to them or not. I liked them because they seemed to be nicer and more permissive than my mom, but that could only be because I was a household guest at the time.
However some of this possible lack of attachment may have carried over into relationships I have people today: I do not readily trust anyone I meet thus I only have a couple of close friends. My sister is a little more trusting than I am, but her hospital stay was not as long as mine. Her thing is that she doesn't get too attached in romantic relationships; ending as soon as they start( of course she it may be because she hasn't found the right person yet).