The 35-year-old had signed a two-year contract with the Crusaders, but has had that terminated after the Welsh club pulled out of Super League.
"We have got a good base here but might have an overload of young players still learning their trade," said Kear.
"It would be nice to get some quality, marquee players in amongst that.
"Keith fits the bill. He has won Super League titles, the Challenge Cup and played for Great Britain on numerous occasions," he added.
The former international has previously played for Sheffield Eagles and Leeds Rhinos over a 16-year career.