Question on how to phrase a certain identity thing

Hi all! Sorry if any of this is untoward or weird, but it’s something I’ve been thinking about.

I come from a very mixed family. I wasn’t raised specifically Jewish, and until recently had no known Jewish ancestry (in doing my family tree I did find that my paternal great-grandmother was descended from German Jews.)

My mom, who was raised Catholic, is married to my stepdad, a Reform Jewish man, who she’s been with for over 25 years (I’m 29), and with whom she raised my sister, who was bat mitvahed and identifies as Jewish. Because my stepdad has been around most of my life, I was raised with a level of cultural Judaism when I was with my mom, I celebrate Jewish holidays as well as Christian ones, and I consider him and his family my family, full-stop.

My question here is, since I don’t feel that it’s accurate to identify as Jewish, how would I describe this relationship with Jewishness? I don’t want to deny my very real connection but I also don’t want to appropriate an identity that I don’t meet. I usually default to saying I’m “part Jewish,” but is that okay to do? It feels overly convoluted to say, “Well I’m not Jewish, but I have a small amount of ancestry, but my mom married into a Jewish family, but she didn’t convert, but I still grew up celebrating Jewish holidays and still do, and my sister’s Jewish, so,” y’know what I mean? Any insight would be appreciated, haha. Thanks all!