Hi,

as long as the frogs don´t differ significantly in size, they will get along given a big enough system. A 20 gal (long) tank will be enough for 2-3 frogs. As ACFs aren´t really territorial, you could keep two males as well as 1:1 (just in case you´d consider to aim for 3 frogs in total, 1 male:2 females or 3 males would be better than 2 males: 1 female to avoid harassment). As for the possible offspring: the frogs will very likely take care of this themselves; just don´t feed them as long as there are eggs/tadpoles
I would recommend to quarantine any new arrival though; a missing eye isn´t necessarily a problem, but there´s always a risk to introduce diseases to your existing system.