First, we need to know if something happened to his mate Gladys?
If so, this would explain why he is hanging around your house. If your husband has been acting kindly to the swan, feeding him, speaking to him, etc., then he is beginning to imprint on your husband.

If Chester is a male, then Ralph is certainly not going to pair up with another male swan. Therefore, Ralph's hormone levels are high due to the time of the year, and he may be looking for another "mate" if something happened to Gladys. Now, there is also a possibility that Ralph is not Ralph at all and is a female and she still likes your husband.

The problem with this behavior as funny as it may seem, is that until the hormone levels subside and go back to normal, you or no one else may be able to get near your husband without being confronted by Ralph. In Ralph's mind, your husband is his best pal and his job is to follow and protect his new friend. So, be wary.

If the behavior continues even after spring time, then this is just a lonely swan looking for someone to pal around. Your husband is his new pal and as long as the bird does not get hurt or other people, then just enjoy the companionship as most humans do not get the opportunity to interact this closely with a swan. Swans are not owned by humans, swans own their human caretakers! The Regal Swan