@Mary ********
you need to head on over to the immigration office and speak to an officer, NOT one of those lackey volunteers that are outside.
IF I was a betting man I'd say NO you can't get a visit thai family extension <- because the thai family you're visiting isn't even IN the country and that's the reason they issue that extension for 😕
It's the same reason as you can't get the "I need my adult thai child to be my caregiver" yearly extension. Your caregiver isn't even IN the country.
I think you got one choice and that's IF you have 800K baht in a thai bank account in your name only for the last 2 months and just apply for a year extension based on regular retirement.
I don't see any other extension option open to you.
BUT
you definitely need to go talk to the immigration office WELL in advance of your current 90 day stamp expiring so you can make a plan <- even if that plan is to exit/re-enter the country 😕 Good luck with it