I guess a lot depends on how the mom is taking it...that would influence the kids perhaps.
Ya I think that is key
If you have to co-wives (is that the proper term?) and they HATE each other, this will obviously effect the children, whether or not the wives live in the same house or not. And if the hate is manifest in other ways (like talking bad about each other in front of the kids), this could also effect the kids. And if the wives are not only angry but hurt and sad as well -again, this will effect the kids, to see their mom in such a state. On the flip side, if somehow the co-wives get along well with other, then this could help create a more pleasant atmosphere in the home and will be better for the children. And also the behaviour of the father would play an important role too. If he is openly favouring one wife or the kids from one wife, then it will have an effect on the other wife and kids