yes, I read a book about Jaco a couple of years ago. His mental decline seemingly happened gradually over many years. Again I think :"What could this man have created if he hadn't sadly died way too early". Sadly we will never know. But what we do know is that Jaco is the father of twins, who are both accomplished musicians. There are clips on YouTube that shows their ability.
Hope we might see some music with Carlos and Jaco released at some point in the future. As the picture in this thread prove, they have played together. Maybe this particular show/jam was recorded? Does anobody know?