Don’t give up! You can kick start it! This happens in lots of marriages. It sounds like you have a beautiful family with well-adjusted children. Don’t give that up for a different set of problems that arise come when parent split.
There are many, many factors that can cause people to feel like the spark is gone and there are many ways to overcome this problem. I suggest this series of articles
http://bit.ly/29u0X14 because I think it sounds like you and your husband just need to spend some time on yourselves and there are great techniques for maximizing that time. This website might be helpful as well,
http://www.5lovelanguages.com/Take the quiz to discover your “love language.” I know it sounds goofy but it will help you learn about yourself. I’m also a big fan of the book Men are from Mars, Women are from Venus. Helped me understand my husband better.
Don’t surrender, fight the good fight and win!