In my first MS I had too many characters. I got rid of the mc's parents, sister, brother in law, and one of her grandmothers. With all of that, I added on great aunt and gave her some of the dialogue that was important to the story that the axed grandma and grandfather had previously, I got rid of a wedding scene that was unimportant so I could axe the siblings, and father from the picture and in the end I ended up with one main character, 5 other characters of consequence, the antagonist, and his mistress, and at a scene with a party, I introduced two other people for the purpose of conversation which would move the plot. ANything important about the girl's parents was developed in conversation with her grandmother, anything that was important from the grandfather was developed through the great aunt and grandmother, etc.
Much smoother without the additional characters. If they can be combined, serve similar purposes, don't really progress the storyline, can be referred to in conversation with other more significant characters, then perhaps that would be the best way to reduce that number.
Good luck!