You cannot join 3 path segments.
What do you want to do? Be able to fill areas? Then you could check out the live paint tool.
my purpose is to cover the extra line that has come out. i can do it with shape builder tool but i just needed to know whether i can join these or not.
You can use smart guides to snap the end points to the other lines, the end will be covered by the thicker lines
thanq both of you 😄
In order to avoid the otherwise ((almost) always) unavoidable change in chape, you can select the extended path, then use the Scissors Tool (guided by the Smart Guides), then delete the extended part.