I knew they were less effective, but I don't remember there being anything about them being unable to soul resonate 

Here is the information about familial bonds and how they work in Soul Eater
From the Soul Eater Wikia
[quote]
Bond Meister

A Bond Meister is a conjectural term given to the type of meister in which utilizes demon weapons via Bond, in which is only possible within two individuals that're biologically related whether it be between parent/child or between siblings. It's also the only sort of meister-type seen in which is utilized by two demon weapons and is the only meister-type in which is unaffected by incompatability, as all family members can wield one another and have an unseperatable "bond". However, a drawback is that Soul Resonance techniques aren't nearly as powerful as one between two different people. [/quote]