In one universe Jack and Ianto had 8 kids.
All named Toshiko.
There was no reasoning behind the name, it just had a sense of familiarity.
This caused complications.
"Toshiko 6, get of Toshiko 1's homework!"
"Toshiko 2, you sister is NOT to be sacrificed!"
"Toshiko 8, if you dare..."
Meanwhile Toshiko 4 sat in the middle of her large, and loud family. Doing her maths homework.
She was quiet, but brilliant, and underestimated by her siblings, using maths and physics to her advantage, against their childish pranks.
Reminding Ianto and Jack of the best friend, they had never met.