Symbolism, Imagery, Allegory
Still skeptical that Mrs. Morel thinks of Paul as a replacement for her dead son, William? Well, it's pretty hard to stay skeptical after Mrs. Morel tells Paul to run upstairs and put on his dead brother's old suit. Dude is literally filling his brother's shoes in this scene:
And as [Mrs. Morel] smoothed her hand over the silk collar she thought of her eldest son. But this son was living enough inside the clothes. She passed her hand down his back to feel him. He was alive and hers. The other was dead. (10.53)
Lawrence shows us here that Paul will never live up to the standard set by his dead brother. He continues:
[Paul] went upstairs and put on the coat and vest. Coming down, he looked strange in a flannel collar and a flannel shirt-front, with an evening coat and vest. It was rather large. (10.51)
How do we know that Paul is going to have a tough time living up to his older brother's memory? Think symbolically on this one. William's shoes are literally too big for Paul to fill, though his mom doesn't seem to mind.