[coupleak]

My sister-in-law and her family.
She, her husband and kids often go to nude beaches, sauna and nude resorts/ campings.
My wife and I also like to hang out naked at the lake, beach and sauna.
However, my SIL never wanted for all of us to hang out naked together. For some reason she found it awkward and weird that her brother-in-law would see her naked.
So she and my wife always stayed dressed, while on a few occasions my BIL and I had been naked while the women were present.

Till 1 day, after 10 years of marriage, the 4 of us went on a weekend away without kids. After a day of hiking, we used the sauna. Guys and girls separately ... sauna cabin was too small for more than 2 anyway.
Inside the cabin, it was pretty warm. The woodstove was keeping the cold outside. But that meant, after being in the sauna, that it was more difficult to cool down and we all kept sweating.
So us guys had already dropped our towels and were naked while playing some bordgames.
Till my wife suddenly said, "well sister, you can stay dressed if you like, but it really is too warm here, so I'm getting naked too." Before anyone could react she stood up right, quickly removed her bathrobe and stood naked in front of us. It was the 1st time my BIL got to see her naked. After that moment, all eyes turned to my SIL and reluctantly she also had to admit she was not able to cool down and even more reluctantly she also got rid of her bathrobe.

Bit awkward at first, but after that 1st time she never again made any issue going naked all together, including when our kids are present.