Well, I can't say for sure; I don't know how you're reacting. Are you taking an ice pick to his knee caps and sledge hammer to his Honda? Are you rolling your eyes and walking away? Are you doing a combo of these things?
Man's eye is prone to wander. Our hearts can be yours, but our eyes are ours; ours to take in and drool over beauty. Believe me it's not fun for anyone. Not fun for the beautiful woman minding her business; not fun for the girlfriend beside us who sees our eyes stretched like a pair of Slinkys down Main Street; and not fun for us, who feel compelled to stare despite fighting back feelings of self-hate for being so predictable and wanky.
But having said all that, there are rules that should be adhered to. Close friends and for certain - family members are EYE-legal. Forbidden. It's 3x ruder,more hostile and nasty to eye-hump your lady's sister or best friend.
So to answer your question: I don't know if you are over reacting but it's very reasonable to have a reaction and discuss it with the Stare-Bear you call a boyfriend. If he doesn't get it, feel free to continually stare at his dad's crotch the next time you're over for dinner.
Stare at his dad's crotch the next time you're over for dinner. Haha, priceless! Very gutsy, too.
I married a man for 14 years and it doesn't change. If it bothers you, it will only get worse. For me, it got to the point where every time I close my eyes when we were intimate, I would see all those young girls and women he rapes with his eyes. I was so disgusted that it was very challenging for me to be intimate with him. He is 42 and was lusting after girls as young as 18 or 20 with his eyes and his mind. Men like this don't change. Looking is one thing, but my ex- practically raped these girls with his eyes and his mind right in front of me.
If you do stare at his dad's crotch the next time you're over, be sure he sees it. For my ex-, most of the time he's too busy looking at other girls that he didn't even notice other men looking at me. Several times I tried to look at other attractive men to see what his reaction would be and he didn't even noticed.
Best of luck to you.