Offer your thoughts or opinion on the input financial query or topic using your financial background.

Is it legal if I'm managing my family's entire wealth?
I am not going to discuss legality, because with family members you are able to give a lot of guidance and assistance without running into legal issues.  The biggest problem is that when they transfer the funds to you and you invest the money, all the tax rates and tax limits are determined by your situation; plus you have more investments than you should have so you hit those limits and brackets quicker. For example: In the United states a person can put $5,500 or $6,500 into a IRA or Roth IRA each year. If you combine the funds for three with your funds then you are giving up three quarters of the amount that you can invest in that type of account. The decision regarding Roth or not depends on age and income level. But now their decision is related to what is best based on your situation. The ability to even deduct IRA deposits would be based on your situation. Of course for taxable accounts the tax rate is determined by your income, not theirs. If they want you to have the ability to make investment decisions for them, then power of attorney is the way to go. The money is deposited in their name, and all the rules and tax rates are determined by their situation. You make sure they have all the information they need to login and review the accounts, but you make the all the moves within and between accounts.