
Nope, If his father was upper moon 1, his father would have to be over 100 years old(I think somebody said uper moon 1 is 300+ yrs old??? Idk) since the upper moons have held their positions for a hundred years at least. Maybe more for upper moon 1. Also the guy Muzan was scared of was the original breath of the sun user who existed hundreds of years ago, it's not confirmed but tanjiro's ancestor was close with the original, probs brothers or besties but they made a promise where Tanjiro's fam passes down the breath of the sun techniques because the original breath of the user had no family or apprentice to pass it down to. This is how dance of the fire God tradition came to be and why Tanjiro's father was insisting on passing it down to Tanjiro, both the dance and the earing which was part of the tradition. Though no one knows yet if dance of the fire God or breath of the sun is one of the same.
Okay--so I've been re-reading this manga for like 2 weeks now and I just noticed this little shit http://www.mangago.zone/read-manga/kimetsu_no_yaiba/nbt/d_v-13-chapter-135/pg-12/ it's the guy who trained under the same master as Zenitsu! The one who chose to become a demon!! Fucking traitor since he was a kid! Oh my fucking god please tell me I'm not the only dumbass who just noticed it.