Why does a family with several children receive only one email?

This is on purpose: Martialnote sends one email per address, so a family is never written to twice.

• For each child, the address is their family's main contact; children of the same family therefore share the same address.
• Identical addresses are grouped, regardless of upper or lower case (a parent who is also a student with the same email counts once).

This is why the preview can show fewer addresses than targeted students (e.g. "18 email address(es) · 25 student(s) targeted"). Each recipient receives their own email; nobody sees the others' addresses.