Answer
What you need is not possible with Illustrator’s path logic.
Paths need to in be a continuous, one-after-another anchor point sequence.
Instead, you can either group these, or convert to outlines, in which case you can join multiple shapes into a single shape, but you’re losing the ability to edit these as paths (unless you keep an un-converted copy).
Attribution
Source : Link , Question Author : Tobias Sutterluety , Answer Author : Lucian