You make Lily a sister.

In lily's menu you now find a tab labeled family. For now it only has her mother in it and a plus sign so you can add more. You could read what information the interface will give you about Lily's mom but that can wait, for now you tap the plus sign to create an extra family member. Then you select 'sister' and a menu opens up where you can select from many templates for her appearance and personality. You could start out with a template of Lily and work from there but you don't want your second creation to end up looking too much like your first one. After some deliberation you decide to make Lily's sister very different from her in both appearance and personality. You decide to pick an athletic template, the same height as Lily but with perky b-cup breasts and a big tight ass that is great but not quite as amazing as Lily's. You spent a lot of time customizing the details on her face, making her have a cute androgynous face that has a bit of a mean expression unless she makes an effort not to. That's when you notice that the gender slider has more then two options, like way more. It has futa, shemale, hermaphrodite, basically every version of 'girl with a dick' that you've seen in media is in there. You decide to indulge yourself and choose hermaphrodite with both sets of genitalia in working order. This gives you the option to select a size for her dick, you want her to be big but not so big that you can't handle it because you do plan on fucking her sometime so you choose seven inches. Satisfied with her appearance so far you continue to her personality.

You start out the same as with Lily by making her kind and caring, but then you make her outgoing, bubbly and flirty. When her flirting has any success she gets quite nervous however as she's a bit afraid of how people will react to her dick. This is why she, unbeknownst to anyone but her (any you because you created her but she doesn't know that), she has even less sexual experience then her sister. Fantasizes about her sister and her sister's girlfriend.

As you liked the filling in the interface did with what you left open for Lily you have faith her sister will be great even in the details you didn't specify. To finish up you make her five years older then Lily, making her six years older then you, call her Tara and give her a job teaching Ju-Jitsu and press the pause button again to resume Lily.