The Ospreys pair both enjoyed superb years in 2008 as they helped Wales to Grand Slam glory, but both have since experienced a downturn in form.
But while Williams will be on the plane to the Republic on May 24, Jones will not be emulating his Lions performances from four years ago this time around.
"We've got 13 Welsh lads going on the tour but the news was tinged with sadness," said IRB Player of the Year Williams.
"I really felt for Ryan because he is a good friend but sadly not everyone can go.
"The back row is the most competitive position on the tour and good players like Ryan, Tom Croft and Denis Leamy have all missed out.
"But Ryan is experienced and mature enough to bounce back. He did the same in 2005 and there's no reason why he can't do that again. He'll be fine."