Various suggestions have been made why Daniel's offspring all died- one explanation pushed by the Zoo at the time was that he carried a 'lethal' gene from his mother Delilah. However many other baby Gorillas were born at Bristol in that era to other mothers apart from Delilah, and they nearly all died too, so such a theory would not explain that. I think it was all just bad management/poor diet etc somehow.
Also Jeremiah would have inherited the gene x2 being inbred-Danielx Delilah, yet he lived the longest. He was very unfit though- always had colds and when he moved to London it was discovered he was nearly blind and had webbed toes.
Susie's son Reuben/Musashi was still alive in Japan a year or so ago, but he seems to be a classic non-breeder who was kept alone for many years, although he has got some(shared?) access to females now. Like the others, Susie also had several miscarriages and stillbirths at Bristol, and also one female baby 'Leah' who died after a few months. (5 in total)
I think Nasibu, who looks fit and healthy, has the best chance of breeding with the youngest Lisbon female 'Anguka' who came from the social group at Taronga Park. I always think if one partner is mother-raised(which Anguka was) there's a better chance of breeding. I'm afraid I think showing Gorillas videos of mating etc would have absolutely no effect whatsoever, despite it being a popular idea. As I mentioned above, there is also some scope for doubt about the parentage of the Kolmarden bay 'Enzo' (and another born just after Nasibu left there)- unless they DNA test to establish for certain they were fathered by their older male 'Efata'
With Longleat's 'Nico' being a wildcaught male with no offspring, I am surprised no more attempts have been made to breed from him, but the logistics do work against any loans/additions so I think unfortnately its a no hope situation.