3 things for me:
My wife and currently 8 month old son.
My dad who almost left us the beginning for 2013
Last year I got back into riding and lost some weight, but it was more for fun and seeing how far I could go more than anything else. After my pops was in the ER at 3 am on the 2nd of January with a racing heart he started just simply watching what he ate. I used to be a pretty strict primal/paleo eater but when my wife was pregnant all bets were off. So now that my dad has lost 51 lbs with some simple walking and eating right, I am not about to get SMOKED weight wise by my old man (tongue in cheek). Plus with a son I realize that I won't be around forever, but I can do things now while I am 29 to ensure I am around for a long time and not miss out on things.
So I have gotten back on the bike, and a MTB, started watching what I am eating, counting calories, riding in such a way to lose weight (like HIIT, pacing myself, getting a HRM) and I am determined to drop 40-50 lbs by the end of the summer. Down 12.5 so far!