Ben, played by 16-year-old Joshua Pascoe, will share a kiss with new friend Duncan later this week - but it soon becomes clear that he is desperate to stop dad Phil from finding out he is gay.
Speaking of the plotline for the first time, McFadden explained that Phil would not immediately accept his son's sexuality if the truth ever came out.
McFadden told TV Choice: "I don't think Phil's more homophobic than the average man. If Ben said he was gay, Phil would think, 'He's just a kid. He hasn't had a relationship. He doesn't know what he is'."
The 52-year-old added that he has been drawing on his own experiences to support Pascoe during filming.
"When I was at drama school I played a gay character and had to take my clothes off on stage," McFadden explained. "I know how embarrassed I was, and I was 25 at the time - Joshua's only 16.
"But it's a great storyline for EastEnders to be doing and I think Phil's reaction is pretty common, so people will relate to it. Coming out isn't just about one person - it's about the whole family."
Pascoe joined the cast of EastEnders last year, taking over from Charlie Jones in the role of Ben.
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