Suggest Stock app

Please Mods I know this question is on FAQ but my requirements are different. So please don't remove this. So guys, I want to open the demats of my family memebers. The thing is that they don't know anything about stock market. I will be handling their portfolio. So, I want to know if there is any good broker where I can login in demat without OTP and just by login ID and password so that I don't have from them again and again. Also Can I add my bank account in demat for adding or withdrawing funds because money will be mine only, so it will be easier. If there is any broker exists, please tell its charges and other pros and cons of you know it.