Who- Katsuki Bakugo x Himiko Toga
Canon Status- NOT CANON
Personal Opinion- Cousins/siblings separated at a very young age
One of the most popular theories is that Bakugo and Toga have the possibility of being related. I somewhat believe this theory. As it is said by fans that they are siblings but, in the backstory of Toga, it is shown that she has completely different parents to Bakugo, so that is where I believe the possibility of family relations is through the possibility of being cousins. So I don't think a romantic relationship for them would be in the cards. It would just be weird and strange in my opinion.