Should I ask?

Awhile ago my parents and I (I’m an only child) were our for dinner and I wasn’t paying attention to their conversation because they were talking about money or something like that. Well I guess I started listening because one of them said the name Tina. Well i didn’t know who that was so I asked them. My dad said “Tina was my first wife”. I had no idea what to say to that so I think I just nodded and I don’t really remember anything else from that night. Well that was a couple years ago (I’m 15 now) but I still remember. I’m just curious and want to know what happened to them and the back story and everything. I’m just scared to ask my mom because I just think that that will be weird and awkward and etc. I just don’t know who else to ask. I should also tell you guys that my dad is VERY overprotective and super strict and he’s definitely not easy to talk to and I wouldn’t want to. It also occurred to me that I may not be an only child. I am from my parents, but my dad could have had kids with Tina and I could have half-siblings. I just need some advise on who I should ask. Please help.