Only if she’s okay with it.

In other words, you can’t just assume (because it’s your “culture” or because you come from a “touchy” family or because you kiss most people you know on the mouth) that it’s alright with her because you like it.

Be about consent each and every time you ask for physical affection.

How?

Asked alone, without any outside pressure from observing relatives to “give in”:

“Hey, big sis, is it okay if I kiss you on the lips?”

And then you abide by her answer.

If she doesn’t mouth kiss relatives, that means no lip kissing for you.

If she’s willing to kiss you in this fashion in certain situations but not others, those are her limits you’re obligated to respect.

Personally, mouth kissing my sister would bring out the Westermarck effect in me, big time.

To each their own.