I don't believe Sule ever gave Sudi and Liwali the same attention. As the next youngest member of the community when Fumo was born; Sule had never seen a younger chimp than himself, so Fumo would have been something of a novelty. While an excellent mother, Kuma was relaxed enough to trust Sule with Fumo, which nurtured their bond. Both Shiba and Lisa (especially Lisa) were more protective with their infants so Sule wouldn't have initially had the same access. Being almost a year older (and therefore more mobile), I'd imagine Fumo was more fun for Sule to interact with. Sembe also showed interest in Fumo. She initially resented her brother Sudi, but soon became an attentive big sister.
Yes, Fumo would be a very young dad if he was Safiri's sire. He was five years and seven months old when Safiri was born (the equivalent of an 10 year old human). Snowy was eight years and nine months old upon the birth of his first infant (Kuma); Lubutu was eight years and five months old upon the birth of his first infant (Samaki); Shikamoo was ten years and three months old upon the birth of his first infant (Fumo). In conclusion, while there probably have been cases of male chimpanzees as young as Fumo siring infants, it is highly unlikely he is the sire when there are so many adolescent and adult males in the community.
Male chimpanzees can tell when a female is fertile and this is when she is of most interest to them. Mating outside of peak fertility is pretty much anyone's game. Sule would mate with females like Koko from as young as five and as long as she wasn't ovulating, none of the adult males would care. Shiba would present to any of the males outside of ovulation; but likely wouldn't present to Shabani or Samaki when she is fertile, nor would they show the same interest that they would in the unrelated females. The likely reason Lubutu was the sire of Lani was that he was the only adolescent/adult male in the community at the time she was conceived (at eight years of age); the next eldest male at seven years of age (Shabani) may have not quite attained reproductive age.
That's adorable. Does Sule show the same interest in Cebele and Safiri?
Has Shabani ever sired any infants?
Do the males have favourite females?