First things first: Talk to your husband and decide if this is really a tradition he wants to continue. If not, then let him lead the battle. But if it’s important to him, you’ll have to come to some sort of understanding.
If it turns out he’s indifferent to the whole idea, then you might want to discuss it with your in-laws. Explain to them that you don’t want to name baby something you might not totally love, just for the sake of tradition. Remember, this is your decision, so don’t let yourself cave under the pressure just to appease other people.
Before you make any decisions, though, consider these options:
Pick a first name that begins with the letter his family wants and pair it with a middle name of your choosing. (Many people go by their middle name rather than their first name anyway.)
Ask your in-laws if they’re open to having baby’s middle name start with the preferred letter, instead of the first name.
Start warming up to the idea and look for inspiration in unusual places. You might actually come across a name beginning with the letter your in-laws love in an unlikely place. Flip open an old yearbook, your favorite novel, or consider the name of a place you’ve traveled to recently.