Proskauer Rose allegedly billed siblings embroiled in litigation over a family trust millions of dollars after initially estimating that their fees would total $100,000 or less, according to a legal malpractice suit filed May 5.

The suit, surfaced by Law.com Radar and filed in Los Angeles County Superior Court, claims Proskauer Rose and Andrew M. Katzenstein, a partner in the firm's private client services department, engaged in unnecessary and excessive work and improper billing practices, such as block billing and charging "unearned, unreasonable, excessive, and unconscionable fees," according to the complaint.