In the KV file, define two buttons with different positions using the following code:

<MyW1>:
    Button:
        id: label1
        size_hint: .2, .2
        pos: 150, 150
        text: 'B1'
    Button:
        id: label2
        size_hint: .1, .1
        pos: 30, 30
        text: 'B2'

In the Python file, define a class as a RelativeLayout reference for the rule of the KV file.

Set size and position for the layout.

As shown here, define a subclass of FloatLayout and add the RelativeLayout as a child.

import kivy

from kivy.app import App...