What exactly did Rebecca want?

If she wanted strong family bonding, then she should be putting more effort than now. This was what Benjamin believed.

How could a family be strong when there were weak links in it?

Benjamin considered himself a weak link because he felt weak when he was with the Sterling family members. After all, Jacob, Shawn, and Louis would never talk with him and would even avoid talking with him. He did not want to talk with Louis, but he wanted to talk with Jacob and Shawn.