How to respond to my sisters questions about past and future partners?

So I’m a cis, bi/pan/whatever identifying woman. I date people of any/all genders and sexualities and gender identities. The majority of my casual partners have all been bi, and I’ve only been in serious relationships with cis bi men and women. My family knows this despite them all being different levels of lgbt-phobic. Now one of my sisters seems somewhat obsessed with the idea that I may date someone who is transgender. Obviously this is possible but I haven’t had any serious relationships with a trans person beyond flings here and there and I only really tell my family about people I’ve been seriously dating atp. Whenever I tell them about a current partner the first thing she asks me is if they’re trans. I don’t know how to respond. I’m currently single again but in the past I’ve just answered honestly because everyone’s been cis. But I feel like that’s giving into her (what I would consider) transphobic line of questioning which makes me uncomfortable. Atp I’m annoyed with being questioned about every date or even friend (because she asks this about most people in my life) I talk about. Idk if it’s better to not respond for everyone or to keep answering honestly. I kinda want to say “I’m not answering that” for everyone I know/date and move on but I’m not sure if that’s the correct action here. I know at some point I may enter a serious relationship with a trans person, which I presume will cause various issues with all of them, but I don’t plan on hiding having a trans partner if/when that happens. So I guess my question is if I should still be indulging in these questions. Should I just keep answering honestly for everyone cis/or trans or deny answering completely. Or if anyone has other suggestions for shutting this line of questioning down??