I've been thinking about your question since you first posted it........ took me back to when I was little, around all my siblings. My BPD mother treated each of us (there are 7) in VERY different ways. Her favorite, who happened to be just a few years older than me-- was allowed to bully and harrass me most of the time. This sister would do horrible things to me and mom would.... oh.... about 10% of the time, when it was particularly cruel-- mom would step in and stop that sister. Could your daughter in-law feel that her son is her favorite? ..... and my mom didn't want her "favorite" to get mad at her(I think that "fear of rejection" came into play)-- so the favorite got away with just about everything.

I don't know though if this really has to do with Borderline...... maybe it's just dsyfunctional parenting?

Anyway-- I'm really sad for the little sister--- I think I can literally FEEL what she is feeling. It breaks my heart-- wish I could help her.

To you Parker for noticing the unbalance-- and to the little sister---

mandy