Your parents could also restrict the financial gifts in some way. They could, for example, give grocery store gift cards that can only be spent on food. Or they could provide a Pea Pod or similar account to BiL where Mom and Dad pay the bills. Any form of financial support, even to family, should be connected to a contract of sorts. Write down the amount to be given, when it can be expected, restrictions on spending it, and when support will end and/or start getting reduced, even if just in email form. Retirement or long-term care planning could be any easy pretense for putting limits on this arrangement. Then advise your parents that, no matter what financial counseling you provide, that these two will probably moan when the cut-off date looms. They may just have to experience some boundaries and discomfort before they are willing to put in the work to change their circumstances.

This has nothing to do with you, and everything to do with mom and dad. The wordsmithing needs to happen there--and then it's really pretty simple. They just need to say, "Hey, we've rebudgeted our finances and we can only afford to pay your rent and $200/month in groceries (or whatever)."

Are your parents asking for help with the situation? Are you aware of their financial status? My ILs are in debt and still giving (36 year old) BIL oodles of money each month to blow on video games and such while he lives in their basement. They know what he's spending it on, but it's their money to give. I think it's stupid, but it's not my place to talk to either party. Everyone seems okay with the situation, and we've made it clear that we are not planning/able to pay for retirement for them.

I think you are trying to be too nice about this. Your parents are being doormats, your SIL has addiction issues and your brother is a moocher. You need to call your brother and tell him to put a stop to this. He needs someone to force him to be an adult. Otherwise, guess who will be paying for your parents' elder care?

I'd send a note to each member of the family thanking them for all the gifts over the years. Explain that although you appreciate them, any future gifts will be donated to charity, as your values have changed and you just don't have the room for any more.

I'd urge your parents to do the same and lower the amount of money they are giving. I'm sure sil will not want to keep giving unwanted gifts that are going straight to charity. Hopefully she won't just change the recipients of her gifts.

OP, it sounds like the issue is that the money for the gifts is coming from your parents.

You can't control what your parents do with their money. While I agree that this is an unfortunate situation, the financial aspect of it is between your parents and your brother and SiL. It is up to your parents to set that boundary about what support they provide and what limitations, if any, they want to place on that support.

Your issue is 100% with your brother who is mooching off your parents.

However, you can not tell your parents what to do unless they want your advice.

OP is upset because her SIL is giving useless gifts to her parents...I understand there's a little more invested here b/c SIL and BIL are living off the parents, but, I think this is a MYOB situation.

If you're hoping she'll chill on the gifts to your family, just emphasize no gift necessary, or suggest something small or consumable if you think she'll insist on b-day and x-mas gifts and such.