There is also the issue of why they are incarcerated in the first place. They have committed no crime, migration and seeking refuge is protected under international law.
The UN universal declaration of human rights is written to be easily accessible and understood by the general public. And given that it was written 75 years ago I think they did a good job. I actually recommend everyone to read it entirely in your native language, as it has probably been translated into it and will only take a few minutes. A beautiful document indeed.
The important thing here though is not how rigorously defined these rights are, but the spirit of the law is clearly saying that the family is a fundamental unit of society. Separating the family unit is a failure to uphold that principal.