So do I. He's been with all the females individually before the birth, but AFAIK not as a group. Mjuku was frightened of him, she may still be so even with backup from the other two females.
Kesho isn't a full-fledged silverback and appears very amiable. I don't think he will be aggressive to Mjuku or interested in the baby either, though he may try and pester her (wanting to play) as that is what males of that age group often do. Whereas their first choice, Pertinax aged 28, (from Paignton) would have probably just sat quietly in a corner and left them alone.
We will only know how it works if they try it....