you can't legally open accounts for your kids that are over 18, they need to do that themselves.

if you wanted to go through the hassle, you could make a trust for each of them, right?

totally

yeah but you could accomplish the same thing as if it were, if that's what you want

My issue is not control. The issue is simply technically opening accounts without separate cell phone numbers. I don't know anything about trusts. What are tax implications of that?

Try fidelity

https://bluewhitefinance.com/invest-for-your-kids-future/ Note that many here fear that because of giyus the money saved in the boy's name will be seized by the state and prefer to keep investing in the parent's name