Connected phones get unlimited calling and texting, and all devices get wireless data access. The devices tap into a limited pool of data usage, which gets renewed each month.
The move follows in the footsteps of Verizon's move last month when it introduced the "Share Everything" plan.
AT&T says its "Mobile Share" plans will debut in late August, but it is keeping its current individual and family plans. Prices will track closely with those of Verizon. One smartphone with 1 gigabyte of data will cost $85 per month with AT&T, compared with $90 with Verizon. Two smartphones and a tablet computer with 6 gigabytes of shared data will cost $170 on either carrier.
The Associated Press contributed to this report.