1) My question is the henna that we take on 7th muharram in Karbala was actually taken by whom from the house of Ahlubait (as)?

2) I have heard that Imam Hassan (as) has 2 sons . One was Hazrat Qasim (as) and second was Hassan e Musna. From both of them one was son in law of Imam Hussain (as) . It is so that Imam Hassan’s son was the really son in law of Imam Hussain (as)?

by

1) No. It has nothing to do with Ahlul Bayt A.S
2) Hassan Al-Muthanna was the son in law of Imam Hussain.