Here's my stab at Sis and Ada...
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Not quite happy with my body morphs, so I'd recommend that you work those out on your own, based on the source art as appropriate.
As for what I used.
Sis:
SASE Nathalie for G8F over at Renderosity:
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For the skin textures AND the face. The body morph isn't a bad starting point, but you will need to do some tweaking.
Hair is Voss Hair, as mentioned above.
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This does seem to be a very close match to me.
Ada:
Skin:
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, also available via the
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Pretty much a dead on match, with some translucency color and percentage tweaks. You can use this skin for her sister as well, they have the same freckle patterns and such, although you might want to need to dial a bit of red into her skin to make it a bit more rosy if you think it needs it.
Face:
VYK Tasmin is fairly close, particularly with the nose shape.
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There may be a closer match.
Body:
VYK Tasmin isn't a bad starting point, but you will need to make a number of adjustments, such as Youth Morph (I went with 30%), and others to taste. Hence, I'd recommend grabbing
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I did a number of adjustments to the body, and so far I'm not 100% happy with it, so hopefully others can find a shorter quicker way to get there.
Hair is Gwenilli Hair of course... which incidentally is a FREEBIE!
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As for Ada's sister, her body shape does seem to be a 'progression' based on age, with the breasts enhanced by a whole bunch, so once you dial either of them in, I'd suggest using that as your starting point for the other sister.
In either case, the skin textures suggested above look to be pretty much dead on to me. As for the eyes, not 100% sure on those, so feel free to experiment with irises from various figures until you find one that you like.
Consider these suggestions as starting points for your own efforts in dialing these characters in. I'd recommend picking up a few morph packs as well, so that you can tweak the breasts, glutes, and such. Hopefully someone with better morph tweaking skills than myself can come up with a decent facsimile.