i realize this is a joke but i kinda also think this is more or less on the money lol. jonathan's virility is baked into the narrative premise of the whole franchise and his role as progenitor thereof; jojo was conceived as a multigenerational saga very early in its development so the inevitability that its protagonist would eventually father children was foregone long before araki even put pen to paper. but it's also not just incidental, there are so many conventional (tbh quite stereotypical) masculine sexual anxieties built into every facet of his arc that i kinda think it all has to be on purpose
jonathan is the only child of noble parentage. his mother is killed in the act of preserving his life; his father lives out the rest of his days as a widower as his love and devotion to his late wife, ironically, renders him functionally impotent. whatever pedestrian grief or survivor's guilt jonathan himself carries over mary's death is compounded by the unique burden of his social standing: he is obligated to the social and sexual norms of victorian high society as well as to the legacy of his ancestors; without any brothers or sisters upon whom to defer the responsibility, jonathan's procreative potential is the last and only hope for his entire bloodline. he has a duty to have children, or else his mother died for nothing!
this underlying sexual anxiety is then complicated by the arrival of dio, who - at least initially - appears to displace him entirely as the favored son. he outperforms jonathan in all contests of filial duty as well as masculinity in general: socially, academically, physically, and most importantly sexually. jonathan's relationship with erina develops rapidly, but chastely; her assault by dio challenges jonathan's manhood directly by cuckolding him (it is imo significant that jonathan never actually finds out what dio did to erina, or that it was not consensual: jonathan is outraged and emasculated not only by his own failure to protect his girlfriend but by his failure to please her). jonathan's obligation to his lineage, past and future, is certainly a burden, but it's also his purpose, which dio's presence (and implied sexual prowess) renders moot. the conflict at the heart of phantom blood is one of "good vs evil" of course, but when you crack it open and examine the insides it's really just an inheritance dispute, and when you crack that one open it's all just male performance anxiety.
accordingly, jonathan's maturation and coming-of-age into manhood is narratively inextricable from his conquest and subduing of dio as a viable sexual competitor. he does not reconcile with his father, inheriting the "golden spirit" and ensuring its continuity throughout his unborn legacy, until after dio "dies" and eliminates himself from the gene pool; the nature of the ripple/hamon, the only force to which vampires are vulnerable, is "life force" (aka sexual/procreative energy); even the more conventional weapons jonathan wields in his crusade lend themselves to the creation of powerfully evocative phallic images:
once jonathan has attained the peak of his manhood and inseminated his wife, he follows his parents' footsteps and dies in the act of protecting his family; by embracing dio in death, he fulfills not only the masculine role of progenitor and protector, but also the feminine role of self-sacrificing provider, resolving at the conclusion of his arc into a kind of idealized, omni-gendered christlike figure of indiscriminate parental compassion and hope for the future (in araki-an terms, we might call this "transcending one's destiny"). dio, whose defeat and decapitation by jonathan has neutered him both figuratively and literally (moreover i get the impression that his vampire biology makes him sterile in the traditional sense, but i don't have any hard evidence to support that it's just a vibes-based assessment), can only reclaim his lost sexual prowess by the possession and exploitation of jonathan's corpse. this, too, is emasculation, in both directions: jonathan is made impotent by dio's sexual abuse of his corpse because he is powerless to prevent it; dio himself is made impotent by that selfsame abuse because all of the children he fathers by jonathan's loins are still undeniably jonathan's children.
tl;dr i would say jonathan joestar doesnt have a "breeding kink" so much as a "breeding complex" and that the circumstances and consequences thereof are the foundation of the intergenerational conflict he imparts upon his descendants that propels the whole plot of jojos bizarre adventure in the first place. When grandma realizes her pussy the reason for everybody in the room dot jpeg
