Hello!
Really it depends on how close in size they are to each other! Mine are sharing a 55 gallon right now and one is 4.5 inches while the other is 5! They've always shared an environment because there's less than one inch of size difference between them.
As well, when you're feeding them try to do it on opposite sides of your tank because it's very easy for one of them to get a little excited and accidentally snap at their tank mate during feeding time.
Perhaps get a tank divider and put them on either side for a few days just so they get used to seeing each other and being close together, then just take it out and keep an eye on them!