If she's so invested, why not ask her to pay for the music lessons? As a holiday/birthday gift to DC, of course.

Op, one of the PPs raise a great point. The owner of the 529 plan can change the benificiary at any time so I would be careful in asking. Also, if you decide to ask have your husband do it.

Nosy.

17:41 here again.

If you want to know, the question should come from your husband with no reference to you when he talks with his sister. I do think there are tactful ways of asking and not sounding greedy or needy.

Here's my perspective for what it is worth. Contribute to your own fund, but I don't think you should deny your children extracurricular activities at the expense of saving for college. Nor am I saying they need to have 16 different afterschool activities either.

I understand the OP's desire to have some idea for planning purposes. We are in the same boat with FIL, who apparently set up a 529 for the kids at birth but has never told us what was in it. I actually asked once when he brought it up but all he said was "a lot."
Since I'm not sure what that means we're just assuming that it doesn't exist for planning purposes.

And if she has kids one day, she can transfer it to them, right? I would ask MIL to ask and see if she will pass along the info. Don't think it would come off the same way from her.

There is no way to do it tactfully. Assume there is nothing. Assume that if she wanted you to know she would tell you. Assume that her life may change one day and she may stop contributing. Assume that if you ask her she may think that you are a golddigging leech and stop contributing.

My SIL is single and in incredibly invested in my kids. She's the terrific and fun aunt that every child wants.
I know that she set up a 529 plan for each of them at their births. I have NO idea what amount she's contributed. It could be $1000 each or $100k.
She has the funds (law partner, no mortgage, few expenses) to do anything.

Is there any tactful way to find out the range of what she is contributing? My husband and have yet to start accounts for our children (in the midst of paying for childcare, etc). We have no idea what exactly our college financial burden will be and therefore have no idea if we have the funds for music lessons now (or do we need to save every cent for college?) etc. etc