Adding multiple items to cart for a specific product

Hello, my apologies if this has been answered before but I couldn’t seem to find the correct answer through the forum. I’m looking for some assistance when adding products to the cart. Here’s an example of what I’m attempting to figure out:

Product A - Exists in my inventory individually and is purchased from suppliers as individual products. However, I would like to only sell the item in pairs. If customer selects quantity 1 on the product page, product is then added to cart as 2 quantity. If customer selects 2 quantity on product page, product is still added to cart as 2. If customer selects 3 quantity, product is added to cart as 4.

Any help is greatly appreciated. Thank you.