Kirby sketched some ideas on some of his projects and Ditko inked some of them; so, it is possible Kirby could have had a couple of ideas and discussed them, via sketches, with Ditko, when Spidey was born and Ditko kind of took the idea and tweaked it to his own sensibilities. I've seen artists sketch out things, then another takes tracing paper and goes over it with some alterations and they go back and forth with a drawing conversation.

The thing of it is, we are all looking at it in hindsight and you tend to look for influences of one or the other that you probably wouldn't see on your own. For instance, we once got a book in our bargain section, at Barnes & Noble, from the UK, which claimed that Andrew and Edward were not fathered by Prince Phillip. It showed photos of the alleged fathers and you would notice similarities; but, the mere suggestion of such a thing causes you to look for similarities and many unrelated people have similar features, because of ethnic backgrounds or body types or what have you. The fact was, though, that the all bore so much of Elizabeth that you coul suggest anyone as the father and you would have to look past the Windsor genes to see it. As it was, I still though Edward bore a strong resemblance to Phillip. I also didn't give much credence to any book that ended up in our bargain section that was never in the trade section, at any point.

Ditko and Kirby shared a lot of artistic influences and origins, so they have a lot of common features within their work, when you look beyond their individual style. So, your preference for or indicators of one vs the other is going to influence your perception.