The actor's character Joey Branning is to fall for his cousin Lauren in an upcoming plot, which kicks off properly next week as they share a kiss.
Witts has now admitted that viewers have always noticed a spark between Joey and Lauren (Jacqueline Jossa).
He told Soaplife: "From the very first time they met, people were coming up to me in the street and saying, 'You fancy your cousin'. So I think it was always obvious that Joey liked Lauren."
Witts added that Lauren will go into denial following a second kiss with Joey at the end of next week.
"Lauren stops and says what they're doing is wrong," the actor explained. "Joey tells Lauren he wants to be with her, but then Max turns up.
"Lauren wants to pretend that none of it happened but Joey doesn't. He knows Lauren feels the same way about him. You can't suppress feelings like that for long."
Asked whether there could be a future for the pair, Witts replied: "I'd like there to be. They love each other and they're not doing anything wrong. It's not illegal to have a relationship with your cousin and they haven't known one another for long."
EastEnders continues tomorrow (October 25) at 7.30pm on BBC One.