Yeah, I combine them using Mesh > Combine. I also smoothed the object using the "3" on the keyboard.
Are you trying to ask me if the 2 objects are going to touch each other? If yes, yes, they're touching each other and yeah, they don't really have to be connected but my problem is I'm want to combine about more than 5 objects into 1 single click and afterwards I'll have to duplicate & modify them a couple of times. So I basically I just want to have them in just one click so I won't worry about leaving behind one piece when I move and modify them as a whole.

EDIT: Oh sorry! I already tried what you've said. I've just realized that "3" on the keyboard and Mesh > Smooth are different. I thought "3" was the shortcut, but it was only a preview. Many thanks! You've added a whole book of knowledge into my head.