It depends on the type of evolution; care only affects child-to-teen evolution. Care has no effect on teen-to-adult evolution within the three main family groups (Ura Mame, Ura Meme, and Ura Kuchi). You could give an Ura Young Mametchi
horrendous care and it would still evolve into an Ura Mame adult. In the Universal family, it's the opposite. Teen-to-adult evolution in that family is seemingly based on care, and skill points have no effect there at all. I'm still trying to figure out exactly how it works, though (it's tough because the Universal family is very difficult to obtain
).
Side tangent: child-to-teen evolution isn't
just based on care, it's also based on what the child character is; for example, KuchiTamatchi and Hitodetchi evolve into Kujakutchi and Ura Young Violetchi with sub-par care, but Kuribotchi evolves into them with very good care. Sometimes it's also based on skill points; Kuribotchi and KuchiTamatchi are more likely to evolve into Kometchi and Ura Young Yattatchi with high Spiritual points and three care mistakes.
Anyway, I hope I helped