Some people have been able to keep pairs or small groups of females or females and one male together successfully. Others have not been able to do so. In the wild, iguanas are solitary animals. They get together only during the breeding season, and then only for short amounts of time. Iguanas do not get lonely for other igaunas, nor do they need an iguana friend.
Iguanas do just fine when kept individually.
As with many aspects of iguana care, the Green Iguana Society encourages owners to learn what they can prior to attempting to keep more than one iguana together. Jake and Donnie are adult iguanas. Jake is male and Donnie is female. They are similar in size, although Jake is heavier-bodied and slightly longer. When I adopted Jake and Donnie, they were four years old and had been kept together since they were very small.