Blotchy brown spots on old cats skin

Hello and thank you all for reading. One of my companions, whom I've had for 12 years,(she is probably 12-13 years old) has developed what look like odd shaped freckles on her head right in front of her ears. Her hair is so thin this is where I am able to see it, I cannot locate it anywhere else on her body although her undercoat is very thick elsewhere so it would be hard to see.
To answer a few questions:
-they are not raised
-She doesn't even know they're there, they do not bother her
-She doesn't overly itch her ears or that area
-She does go out in the sun and lays in the grass to bask in the sun, but has since she was a baby and never developed these spots until lately
-her catsister who is a different breed, and who is only about 10 years old, has not developed anything like this.
-her dogsister feels the need to constantly lick them and lick her face which she never used to do.

Is she just getting old and her skin pigment changing? Could this be cancer? Should I take her in? Or should I not worry? Thanks in advance for any knowledge .

I think if you notice anything new it's worth a call to the vet. Maybe you can show them some photos.

So it's probably not cat freckles from being in the sun? :-)

you can ask vet but if its not red itchy or raised it may just be sun spots.

My cat Wiggies has the exact same thing, but he's always had pigmentation patches there. He has a few including a patch on his gums. The vet has never been concerned with them. However, he has always had them, not just developed suddenly. This is what concerns me with your cat. Plus your dog's sudden attention to the area - they can detect the chemical changes in bodies caused by cancer or other illness. For your peace of mind, I would take her to the vet to get them checked.