Bright Horizons Inc. and Corporatefamily Solutions Inc. agreed yesterday to merge in a stock swap, in an effort to snare a bigger piece of the growing market in child care offered by companies. Bright Horizons shareholders will get 1.15022 shares in a new company called Bright Horizons Family Solutions for each of their shares. Investors in Corporatefamily Solutions will get one share for each share held. Bright Horizons had $85 million in sales last year while Corporatefamily Solutions had $77.7 million. Corporatefamily Solutions, based in Nashville, has 100 centers in 29 states. Boston-based Bright Horizons has 155 centers in 29 states. Shares of Bright Horizons rose 12.5 cents yesterday, to $27.375, while Corporatefamily fell $4.125, to $26.