I don't have sister. But I have seen my mom doing peshab while we were on a long journey and she had to do emergency moot behind a jhaad. I had Watchman duty to stand near her to lookout for people. Through the side of my eyes I saw her panties pulled down to knee . As she was sitting low, gaand was not visible.I had the paper tissues with me for her to clean after urination. She was very shy to take the tissues from my hand. She half stood up to wipe and then quickly pulled up panties, saw a bit of thighs at that time. We walked near the car and her cotton saree didn't fall down properly. She was blushing with shy when she asked me to help her pulling down her saree to hide petticoat. While driving we didn't talk for a long time as we were finding difficult to face each other.