A source told The Sun: "It's my opinion that Harry feels he couldn't protect his mother, so he's going all out to protect his wife. This is his way of atoning. He will brook absolutely no criticism of Meghan — and he is so sensitive he often sees criticism or negativity where there isn't any."
After meeting Markle for the first time, William reportedly sat Harry down for a chat, imploring him to take things slowly.
"William told his brother they knew nothing about her background, her intentions, what she was really like," a source said. "He just wanted to stress that becoming part of the Royal Family is a massive undertaking and the pressure and scrutiny is unrelenting. Was Meghan the right one?
"Harry went mental. He accused his brother of trying to finish his romance before it had begun. The brothers' relationship has not really recovered...Harry stood up for Meghan very forcibly. He really loves her."
As a result, Harry is reportedly quick to jump to his wife's defence whenever he feels she's been treated unfairly.
In February, the two couples appeared on stage together for the first time to talk about their Royal Foundation charitable work and their host asked them if working together as a family caused any "disagreements".
William answered: "Oh yes," and Harry added that the clashes "come so thick and fast."
When asked if they'd been "resolved", William replied: "We don't know!"