What the fuck are you talking about?
The first "hole" joke is, yes, their "earholes" shared an earbud. They both stuck that same piece of equipment in their same "holes" (ears).
The second joke is not a joke so much as a crass reference to sharing a mother's vagina. Because she's making a metaphor about being sisters (who come out of the same vagina; their mom's). Which she corrects herself and decides, no, they are actually more like mom/daughter than sisters.
Or am I missing something from your own post?