Moving my cats

My husband and I recently decided we need to move in with my parents for a while to save up money. It will be good for us, the only problem is we have 3 cats and they have 2 dogs and live in a very small house. My older sister lives next to them, and offered to take 2 of our cats, Steven and Flora, who are inseparable, and we will keep our oldest cat, Onyx. Onyx doesn't really get along with/Like Flora and Steven very much, they're very hyper and crazy, whereas Onyx likes to sleep and be alone, but he will usually still hang around the other 2 if they're in the room. My worry with them moving is Onyx will get depressed or lonely. Has anyone went from 3 cats to just 1 and have any issues with it??