Could he be talked into riding with you? Before my hubby talked me into trying cycling I didn't particularly like the money he spent on bikes...or his need to have at least 3 (road, mountain, cyclocross).

Then I got my first road bike (which I upgraded a year later to something more suitable to the sort of riding I liked and with better components)...and the rest is history. Now I have 3 bikes (well, I did--before my kiddo took over my mountain bike, so I will be upgrading again, soon). Hubby has 4 (road, mountain, CX, fatbike), kiddo has 2 (CX and my former mtn. bike) and we have a tandem...which is mostly DH and DS's so we can all ride on the road together.

I'm sure to some our # of bikes would seem excessive, but we don't have the sorts of $$ toys that a lot of folks near us have, like boats, jetskis, snowmobiles, ATVs or horses. We don't take many vacations, and the ones we do are generally rather short and close to home or to visit family. We have a cheap old house with a cheap mortgage. We drive relatively economic cars and drive them for a very long time.

If you can't talk him into joining you on a bike (and seeing why n+1 is serious!), then I think the relationship angle is the important one to address. Even if you were to convinced him to join you, that's a good conversation to have.