Mr. Cranston is married to Mrs. C, and dad to Olive and Camilla. To tell you the truth, we don't see much of him since he stays behind the scenes most of the time. Mr. C's one shining moment is when he catches Lady Augusta as she faints at the princess's shindig. So while he may be in the background most of the time, this heroic gesture earns the Upstairs Cranstons some (much needed) brownie points with the rest of the ship's passengers.
In addition to being a one-time hero, Mr. Cranston is also a pretty angry bloke. His biggest scene in the story is basically him yelling at his wife and daughters about Olive and Camilla getting hitched:
Fumes seemed to rise from Mr. Cranston. Sulfurous fumes. "Six months?" he said in a low and dangerous voice. "Six months?" Once again he rounded on Mrs. Cranston. "Woman," he said, "you seem to forget this whole business was to get Olive off our—to get Olive married. NOT CAMILLA!" (13.27)
Hey there, raging temper. Just look at how Mr. C manages to be rude to everyone in this scene. He's mean to his wife and to his daughters in just a few short sentences… and he's not about to apologize either.
Mr. C only shows up a couple of times in the book, but it's pretty much the best and worst of times when he does.