If you put your family members on the same account all calls between you are free. Even if you are thousands of miles away as koodo has nationwide plans. Since all plans now come with unlimited text messaging the only thing you need for individuals is data if you use any.
If by family plan, you mean sharing minutes and data usage, then it is not available with Koodo. As Chris mentioned, you can place all members on one account and be able to have unlimited calls in Canada between members on the same account.