Well actually, the point at which children start bonding with their parents is at conception. For 6 to 9 months before birth, babies bond with their mothers and whatever siblings in the womb, and can recognize their scent, touch and heartbeat. As proven by statistical and anecdotal evidence from adoptees, separation from their mothers and/or siblings, even at the time of birth, can be very traumatic for these babies and can cause serious life-long mental health issues. So I would say that Luke and Leia were traumatized by their separation from their mother and from each other and I wouldn't be surprised to find that they did have mental health issues growing up, which probably exacerbated their psychological issues from their adulthood trauma.