I'm just curious to know if there is any difference between

[1] I'll join you,

[2] I'll join on you,


[3] I'll join up on you


Any and all your help would be very much appreciated.

2 and 3 are kind of strange to me, but I've found several instance of 3) on the Web.

However, the established usage is:
Phrasal Verb: join up

To enlist as a member of an armed service.

Phrasal Verb: join up with someone

To come together with them for joint action, etc.

i know that, to use "join", you should say A join B
but for "join up", you should say A and B join up.
however, i haven't ever seen "join on" ..
 Marius Hancu's reply was promoted to an answer.