One cat growing much bigger/eating more than the other

[pinotnow]

I have a sibling pair of around 5 months old and have had them for just over a week. It really hit me today how much bigger the boy has become just in the time I've had them, and the same is not true of the girl. She is noticeably skinnier than him and, while he was always a bit bigger then her, the difference is much more pronounced now. They eat together but she tends to pick and lose interest quicker. I think this evening she has had round about 1/2-3/4 of a pouch and he has had a full one and is itching to get her leftovers now. I will try and feed them separately but it's not easy as she won't eat it in one go so I have to keep watching he's not going back to it while it's still accessible to her.

To be fair I have an older female cat and used to have another male and it was the same dynamic with them, though they didn't come as a pair and were adults when I got them but I was always having to shut him out while she ate as far as I could. But now I'm worrying that she isn't growing enough.

No advice, but this is how we ended up with our lovely boy - because he was wolfing all the food and starving his brother! He came to us at 15 months and was a wee fatty, but now regulates his food intake very well as a single cat. He’ll be three in January. Both kittens were stray and living in a lady’s shed until she brought them in when the weather turned (she still has his brother) and I guess he was used to fighting for food.

Same as with people, you can have full siblings who are very different in physicality and personality. Also (NOT common in humans!) you can have different fathers within the same litter with cats.

DSis had a similar problem when she adopted 2 young mothers not long ago. One was a greedy fatty, the other tiny and rather thin. She started feeding them smaller but more frequent feeds, so instead of say half a pouch each twice a day she'd put down 1/3 pouch each 3 times a day. That way the smaller one who ate less at one sitting would get to eat her whole pouch per day, and the greedier one didn't get extras from the other's left overs. Obviously she left dry down as well.

Fatty cat no longer waddles & is much more agile, and skinny cat is no longer skinny and despite being around 18 months when she came home is now a bigger cat in all dimensions not just filled out.

Microchip feeders are the obvious solution here, I recommend the surefeed one, you might just need one if the other cat is not a grazer.