If the partner is a good friend of yours, the answer is simple... pay a reasonable amount for her services, take it as a lesson, and clearly define these things in the next deal. You're still making money, but in my eyes (and many others), it's not necessarily a fair deal on your side due to the higher financial contributions/stake in the game.
As for paying your family interest, you absolutely should do that even though they didn't ask for it. It's the right thing to do, and they came through for you when you needed them to... pay them rent on their money and keep the avenue open for future projects.
Deals can be a one-off, or you can have continued relations with those you do business with. Take this as a lesson learned and move forward, with your friend making out slightly better than you.
The alternative option is to fight it and ruin a good friendship. I somewhat question your 'friends' view on the situation though, on the flip side, I would be eating my wifes' design fees and would pay for them out of my share of the profits... again to preserve the friendship/relationship. As he's unwilling to do so, I question his friendship/loyalty.
Best of luck.