Astarotte no Omocha!, Papa no Iukoto wo Kikinasai! Recommendations
it's not THAT similar, it's just that both anime has a guy that's, for Astarotte IS a father, and in papa is just kinda like a father, both taking care of a child. Astarotte isn't a story about that though, papa is more of a family story, and Astarotte is more of a romance stuff
They're both loli shows that are surprisingly decent by being somewhat heartwarming.
Both have adults(teenager in PnIwK) taking care of kids, both are ecchi, and a harem if you think about it.