Are my Guinea pigs sisters?

Hi 👋,
I’ve recently become a first time Guinea pig mama to two adorable little Guinea pig girls. When we got them from the pet store they told us they were sisters which I believed since they were the same size and similar coloring. However, over the course of the few weeks that we’ve had them I’ve started to notice some apparent differences in them. One seems to look and act much younger than the other one. And when I looked up guinea pig breeds online it appears they may even be two different breeds. The one on the left with the white stripe down the nose looks older and is much more afraid and from the looks of it looks like an “American guinea pig” breed. While the one on the right looks and acts younger and more playful and friendlier and appears to be an “American White- Crested guinea pig” breed.

So my question is: do you think it’s possible that these two really are sisters if they appear to be different breeds and different ages? Maybe they have the same mother but came from different fathers?
Would love any opinions if you got one, thanks!