As Britney Spears' and K-Fed's toddlers are reduced to sending desperate S.O.S. notes to celebrity glossies via the carrier pigeons who have become their only friends and lifelines while encased in a chicken-wire prison in their mother's home, their quarreling parents continue to up the ante in the messy and contentious battle over who'll win the right to neglect the children full-time. In the latest development, K-Fed's lawyers served Spears' cousin and assistant Alli Sims with a subpoena to testify at the divorce hearings. (Watch the electrifying serving of the legal document in question here.) Federline's lawyer wouldn't offer details, saying only that Sims was "believed to have relevant information" regarding the case. Since this was the very same Alli Sims who reportedly sat back and did nothing as Britney shockingly tossed back glasses of post-rehab sake and wine, and more recently held a front-row seat to Britney's erratic OK!-photo-shoot transgressions, who better, then, to testify at Tuesday's custody hearing how the singer has been neglecting her kids in favor of cherished new family addition: couture-despoiling rat-dog, London?