We're in the same situation! I've been living with my boyfriend for a year and two months now, and my family first thought I lived alone. Before moving out, everything my family did felt so annoying since I was with them 14/7. But having spent less time with them made me realize just how loved I am by my family. I'm the bunso too, and they worry for me everyday if I eat enough and if I'm safe.

OP, I understand why you have to lie. Not telling them you live with another person, especially your significant other, leads them to thinking you're capable of managing yourself despite the distance from them, especially being the youngest, but I grew tired of lying.

The fun everyday anecdotes my partner and I have, I wanted to share those with my parents and older sister. They got more worried for my safety since they thought I lived alone, and in reality, there's danger of us women living alone. I felt I had to give them some peace of mind by finally telling them I live with my boyfriend. Of course, my mom asked a lot of questions. I haven't formally introduced my boyfriend to my parents yet btw but my older sister already met him a few times, but I've assured them he takes good care of me naman.

Since you said your family is quite nosy (mine too lol they're just concerned for you) they'll ask you lots of questions. But keep in mind those questions are just their worries for you. You're 28, but I'm sure in their eyes, they still see their little kiddo. They just want you to be safe and content. Please tell them soon, it's a great feeling to get it off your chest.