Two Sigma Securities, the market-making affiliate of the $30 billion hedge fund firm, is growing its brokerage business. The New York-based firm is acquiring the US options-market-making business of Timber Hill, a subsidiary of Interactive Brokers Group. The deal, which is expected to close in September, will expand TSS's offering, spanning 7,000 US stocks and options on 1,300 underlying securities, Two Sigma said.