After my first set of lovely foster kittens, I got a 2nd set where two abandonned kitties were added to the litter (yes, they look different), and the mother was accepting enough to fed all 6. The smallest one was very small and a bit sickly when I first got it, and was weighed every few days until she finally was able to eat solid food.
the mother was very nice and nicely agreed to feed 2 kittens that weren't hers
the whole family of 6 kittens
Eventually, it was time for a fair amount of travel, so I had to give them back for them to go to the next foster family, but that month was a lot of fun: