If one has gained alot of weight or both have gained alot of weight then things don't fit like they used to and it can become work. Hence, not as enjoyable.
Adventurous? Sometimes with time, kids, work and life, adventures have to be planned. Catching up on a little sleep may seem easier and better than a frolic. Take some time for yourselves and get caught up a little and plan something. And with adventure it takes two tp play, so don't blame the other, blame yourself more.
Your sex drive belongs to you not your spouse, you are responsible for a low sex drive. If they have a low sex drive you just ain't getting none.