Couples Party

You and your partner are hosting a party for couples. You have 8 guests (4 couples) over for dinner, for a total of 10 people at the party (including yourselves).

Not everyone knows each other at the party, and you and your partner don't necessarily know everyone either. At some point during the party, you notice that the 9 other people there (including your partner) know a unique number of people at the party.

Each person knows at least their partner, and knowing someone goes both ways (i.e. if A knows B, then B knows A). How many people do you know at the party?

Source: unknown