I too think it is an object constancy issue, and it's something I've been experiencing in therapy, too. T is the 'object' of your affection, but it doesn't mean it's in a romantic way.. (I think sometimes it's this conclusion people leap to, because as adults we can maybe only relate the experience to 'falling in love'.. what else can it be?!) I believe though, that it is at least in part down to attachment - feeling as a child would towards its primary caregiver.