Kirchhoff's laws for voltage in parallel circuits

I think I understand his current law fine, but how do you apply his voltage law in parallel circuits? For example, in this circuit



If you know the battery is 9V, then you could look at the "top loop" and figure out that the bulb also has 9V across it
But if you look at the "bottom loop", since voltage is the same everywhere, and there are two bulbs in that loop, wouldn't it add up to 18V? Since they're both taking up voltage, isn't the sum of the potential differences in that loop not equal to 0?

Bottom loop. If u take an anticlockwise loop, the top bulb is + V while the bottom bulb is - V. Add up to zero. From the bottom loop can only deduce the pd across each bulb is numerically equal to each other.

But since from the top loop u deduced the top bulb is 9 V, That will suggest the pd across both light bulbs are 9 V.

The right side of the bulb is negative and left side positive (same as the batt). Going anti clockwise, top bulb you are “moving” from negative to positive and thus its a rise in potential . Bottom u r “moving” from positive to negative and thus a drop in potential

Well firstly, you don't need Kirchhoff's Law's to actually answer a question like this. There is only one source of emf, the cell, and you just have 2 resistors in parallel in the circuit.
The voltage law says that the (vector) sum of the pd's in a closed loop is zero. But the important point is you have to take the direction of the pd into account in the loop.
Is the pd pointing clockwise or anticlockwise within the closed loop?
Assuming no internal resistance.
In the lower part of this circuit, the pd across the lower bulb is in the clockwise direction in the lower loop. (The Plus on the left)
The pd across the upper bulb is pointing in an anticlockwise direction in the lower loop.
The 'sum' of these two is zero as they are in opposite directions in the lower loop.
This is correct as there is no source of emf inside the lower loop.

Glad i could be of some help! Anw, it may help to know that potential is a scalar quantity and thus algebraic sum may be a better choice when u are stating KVL

It's not 'potential' it's potential difference here.
And as such, in a circuit loop, has an implied direction.
The use of the word 'vector' here is simply saying that you need to take this direction into account.
Thanks for helping to answer this question.

Thanks for clarification. May i just check, so potential difference is a vector quantity?

Not in the same sense as normally implied. No.
The point with pd in a loop, as we have here, is that it can be clockwise or anticlockwise, and as such has 'direction' for the purpose of addition in Kirchhoff's law.
It's exactly the same consideration as 2 cells with emf 1.5 V placed in series. What is the total emf here? 3V or 0V?
You have to take into account the 'direction' of the cells (and therefore of their emf) in order to 'add' them together.

Thanks! One last qn, this definition can be found in which exam board learning objectives/syllabus?