Well I hate to say it but there will always be some comparison, its only natural as person. The best way for you to view it is that you are going to be different from anyone else. That does not mean necessarily better or worse just different. for example I can enjoy both apples and oranges equally while still comparing their differences. what I'm getting at with this is its a POV.

I would suggest starting with group dating so that you are spending equal time with her to begin with. You can also set up a discrete gesture to let him know its time for him to pay attention to you, and vice versa something like squeezing his hand.

He may also start to feel jealous, wondering if he is unable to satisfy you. He may ask himself why you need someone else, so reassure him that he is your man and spend some alone time with him if he starts to look uncomfortable.

Go slow to begin with and make sure you are both comfortable every step of the way. Good communication is necessary.