Yes, children are still sealed to there parents after they are sealed to their spouse. Just like a son or daughter is still as son or daughter after they are married, they just become a spouse to one person as well as remain the child of there parents.  
 
Yes, it is like links in a chain that connect all of us all they way back to our first parents Adam and Eve, we will all have the chance to be sealed to all our anestors even if that chance only happens after we out of this world and are in the spirit world.  
 
Most of the temple work will not be able to be completed till after the second coming of Christ, when our righteous deceased ancestors will be able to assist us to fill in the missing ancestors of ours families that unfortunately were forgotten in our recorded history.