Are you boring?
This isn't the insult it sounds like. Recently I was having lunch with a cousin and a cousin in-law, and my cousin (food blogger/cookbook writer) and I started an intense discussion of how to get a sauce to emulsify - add slurry? gelatin? egg yolks? We went on and on until we noticed our in-law's eyes glazed over.
Do you talk about food too much and bore the pants off your friends and loved ones? I know I do! I've been reading books about cheese for the last month, and I think if I bring it up one more time my husband will file for divorce. I guess it's the same as being stuck with fantasy-football enthusiasts, or two people who just Netflixed Lost and can't stop theorizing.
Conversation is an art, they say, and the art of it includes paying attention to everyone involved, to make sure that they all *are* involved and interested in whatever you're talking about. Sounds like you and your cousin didn't do that, but ignored your cousin-in-law as if he (?) wasn't even there. That's not just boring, it's discourteous and unfriendly.
Even worse is having a conversation with somebody who isn't even there, by cell phone. But you didn't ask about that.
I try not to bring up food (and a couple of other topics). I will, of course, contribute if someone else starts that conversation.
Oh, I know I do it to DH..."wanna hear what they said on Chowhound?". "On Chowhound, someone asked about bla bla bla.."
Though if there's a good clever repartee going, he will let me read the whole thread to him aloud. ( This is especially fun on multi-day road trips). Lucky for me, he is a great audience and a quick wit.
When doing any type of "techno talk" I always do my best to draw in everyone in the audience. It usually works.
Then again my lovely wife is a computer geek. Two of them get together and: "DBA, Cobal, *$#(^)*&)(*&(*&^*&$&$!!"
I look around and grab the first person who's eyes are glazing over and start talking about food.
Hubs is a computer geek, too, and when he gets wound up, I start with my psych-speak ("trichotillomania's prevalance and the culture-bound syndromes"...ad infinitim)--usually helps to break his chain of computerese.
I have, though, hit his limits of tolerance with my recent specs recitals of the KA I'm getting next week. However, he's also shopping for computers, so we're cancelling each other out.