I just recently joined CABE, and happened on the forum AND this discussion by accident. First, my opinion is I think the OP ought to list a name, location, etc.
It's an interesting topic.
I'm Gary, wife and I (age 66 & 65) live in central Va. on a small farm.
We've loved bikes for 60+ years. It was a way to visit friends, especially farther away, and work (paper route).
Lots of people collect things. My brother it's stamps and coins, parents collected antique clocks, personally I love anything mechanical.
A bicycle is a combination of mechanics+art+exercise. We have 60+ years of memories and experiences.
I still have my Schwinn Le Tour I bought in the early 70s. I rode triathlons back then. In the mid 70s while riding to visit my now wife I was going about 35+ when a truck cut me off, I had no helmet, reaction was to slam on brakes and I catapulted into pavement...head hit first.
I immediately bled out my eyes, mouth, nose, ears...rushed to hospital...family told I wasn't expected to live...massive concussion.
But, I made it. It wasn't the bikes fault (even the truck driver wasn't charged!).
Bottom line, the OPs brother in law collects bikes. They happen to be larger than stamps or coins. He's harming no one. He's not (I assume) going to bars, running with women, he has a harmless (and valuable) hobby.
Why not tell him politely it's not your interest but as long as it doesn't interfere with your sister's life...he's right there at home, they have food and home it's completely harmless.
I should be so lucky to have a brother in law like that.
Sent from my SM-S320VL using Tapatalk