I'll be using Servine, Riolu, Ponyta, and of course Braviary and Shuppet as merge pokemon.
Lol Ponyta. She'll probably look like a centaur or something.
Which means I have 5 new characters to introduce, meaning I have 6 total with 4 merges and 2 non-merges, (3 merge non project members and 1 non-merge project member. One each of project members.)
I'll introduce merges according to your rule of 10 pages.
Laura Kima (Shuppet/Braviary Merge) - 13
Lindsey Kima (Servine Merge) - 14
Erina Green (Ponyta Merge) - 15
Erin Green (Human) - 15
^^Fraternal twins that would be identical in every way except they're opposite genders
Alexandra Red (Human) - 16
Alexander Red (Riolu Merge) - 16
^^Fraternal twins, same as Erina and Erin
No, they are not intentionally in age order.