TMZ spoke with Leicester Bryce Stovell's younger brother -- "Junior" Stovell (pictured center) -- who tells us, "something's a little fishy" about Leicester's allegations.
As we first reported, Leicester filed a lawsuit against LeBron and his mother Gloria James, claiming they tampered with evidence that could prove he's the daddy.
"Junior" tells us his family has been "joking" about the situation ever since Leicester suggested he was the dad a few years ago -- but notes that Leicester “believes in his own mind” that it's legit.
As for why "Junior" thinks the story is fishy ... he tells us, "Leicester never mentioned anything about LeBron being his son until LeBron became the king."
LeBron's camp has strongly rejected Leicester's claim -- calling him a "money grubber."