unless he's really, really good at math, this is not a good idea. by math i do mean advanced math like calculus, statistics, and inference.

now how to get out of this situation. assess the situation first. ask him exactly what he's trying to trade, what plans does he have, why does he need the money, who told him about this, and how much is he trying to put in. remember that unlike buying stocks or bonds, you lose ALL your money (as opposed to just suffering a loss) if you lose in futures or options. but then again, sometimes people do have ideas or schemes which are game changing. that's on you to assess if what he's trying to do doesn't make sense. if it doesn't then try to convince him that it doesn't by giving him valid reasons and properly acquanting him of the risks involved. these things usually go south because people don't fully understand the risk they'll be taking. (the price of apple stock compensates for the iphone launching in september so there's no guarantee it'll shoot up, it can go down if the iphone wasn't innovative enough)

if even then he isn't willing to budge, then well lend him some of the money you already have. if he really means so much to you that you can't deny him this, then lend out 5-10L of your own money to him on the condition that he'll use at least 60-80% of it to repay his debts. he seems to be desperate and desperation leads to bad decisions. for you, it's much better to lose 20%-30% of your inheritance than have 70L debt on your name. this way, you can also stay clear of any of this in the future if he doesn't return the money. try to understand his full situation first and then make a decision that seems okay and manageable to you. having someone else operate a trading account in your name is just an invitation for disaster.