Here are the specific rules you need to follow to get a non-Mixed Family:
1) Raise one of the following characters.
Mametchi
Memetchi
Flowertchi
Kuchipatchi
2-A) If you will be using the matchmaker.
Your character's Bonding Level must be 100%.
Select the marriage partner as follows.
Your Mametchi + matchmaker's Chantotchi = Mame Family
Your Memetchi + matchmaker's Mumutchi = Meme Family
Your Flowertchi + matchmaker's Sukatchi = Flower Family
Your Kuchipatchi + matchmaker's Yonepatchi = Kuchipa Family
2-
In the case of a love marriage (by connection.)
The marriage partner must visit your character to mate on your Tamagotchi toy.
Do not send your character to the partner's Tamagotchi toy to mate there.
Either character's Bonding Level must be 100%.
Select the marriage partner as follows.
Your Mametchi + their Chantotchi = Mame Family
Your Memetchi + their Mumutchi = Meme Family
Your Flowertchi + their Sukatchi = Flower Family
Your Kuchipatchi + their Yonepatchi = Kuchipa Family
Note: I'm sure only of the family name "Kuchipa" Family since I have had that on my V5. The others are a guess at the English names, since I've translated them from the FamiTama / Japanese names.