During Luffy's origin story, Shanks and Makino did seem to be friendly with one another but not too friendly. However, post-timeskip, a cover page revealed that Makino eventually did have a baby and that the baby was probably "his."Whoever "his" was is still up for speculation, but a major fan theory is that the baby is Shanks', given the fact that there aren't many other major male characters around Makino's age who she's interacted with. With this ship in mind, Shanks' time on Foosha Village definitely has a lot more going on than just taking care of Luffy.
