The Ryerson family was only on the Titanic because Arthur Ryerson Jr. had been killed in a car accident; the family cancelled their European plans and were returning for the funeral. By all the accounts I've read, Mr. Ryerson was totally crushed, and unlikely to play cards at any time, let alone when his family needed him.
The story of Lifeboat 4, on which many famous Titanic families survived, is worth a book in itself. Mrs. Astor, the Carters, Mrs. Walter Miller Clark, the Ryersons, Mrs. Thayer, and Mrs. Widener all ended up on this lifeboat. Mr. Lightoller's loading of these passengers is a not tribute to his organization skills. It was one of the first lifeboats to start to launch and yet one of the last to actually hit the water, and yet it was still only half full and no men were allowed aboard. (Other than the Collapsibles, Lifeboat 4 also had more people rescued from the water than any other.)
Lightoller, who sounds totally overwhelmed at this point, wasn't even going to allow young Jack Ryerson aboard. Mr. Ryerson, who had just lost his namesake a few days before, was not about to lose another. "Of course that boy goes with his mother. He is only 13 years old," he objected.
Anyway, to make a long story end, I can't see Ryerson being a fourth.
There were quite a few card games going on. Some groups seemed to have 5 and some 3, but I don't recall any looking for a fourth.
