Pretty simple, you put in any name you think fits the style, meaning, etc. of the other twin, and I pick first place (3 points), second place (2 points), and third place (1 point). Part 2 will come later if there's enough interest in this one - giving MNs to the first place picks.
1.
Arthur and _______ (sister)
2.
Lucy and _______ (brother)
3.
Caitlin and _______ (sister)
4.
Callum and _______ (brother)
5.
Raphael and _______ (brother)
6.
Orla and _______ (sister)
7.
Saoirse and _______ (brother)
8.
Tatiana and _______ (sister)
9.
Ewan and _______ (sister)
10.
Eugenie and _______ (sister)
11.
Sandrine and _______ (brother)
12.
Matthias and _______ (sister)
13.
Hugo and _______ (brother)
14.
Lachlan and _______ (sister)
15.
Lola and _______ (sister)
Also, I think most of the genders are pretty non-unisex, but ask if you need clarification.