Traveling With Brother-in-law
There is nothing Haram in that as long as both observe the norms of gender interaction as explained in Quran, Surah Nur ( Discussion 30301 ). However, meeting of two people of opposite gender in seclusion has been highly discouraged on the basis of Sadd-e-Zariya. Since Zina has been considered as grave sin in Islam, therefore all the means that may lead to such an act, should be avoided or discouraged at the very least. But this does not mean, we should give fatwa of Haram in case this happens, because sometimes such situations or meetings cannot be avoided. https://youtu.be/zO2KrEWEgJ8